Air Heater
Air Top 2000 S D (Diesel)
Air Top 2000 S B (Gasoline)
Service and Repair Manual
– Improper installation or repair of Webasto heating and cooling systems can cause
fire or the leakage of deadly carbon monoxide leading to serious injury or death.
– Installation and repair of Webasto heating and cooling systems requires special
Webasto training, technical information, special tools and special equipment.
– NEVER attempt to install or repair a Webasto heating or cooling system unless you
have successfully completed the factory training course and have the technical skills,
technical information, tools and equipment required to properly complete the
necessary procedures.
– ALWAYS carefully follow Webasto installation and repair instructions and heed all
WARNINGS.
– Webasto rejects any liability for problems and damage caused by the system being
installed by untrained personnel.
Air Top 2000 S
List of Contents
List of Contents
1.
Introduction
1.1 Scope and Purpose.................................................................................................................................101
1.1.1 Use of Air Heaters.......................................................................................................................101
1.2 Meaning of Warnings, Cautions, and Notes............................................................................................101
1.3 Additional Documentation to be used......................................................................................................101
1.4 Safety Information and Regulations ........................................................................................................101
1.4.1 General Safety Notes..................................................................................................................101
1.5 Legal Provisions for Installation...............................................................................................................102
General Description
2.
2.1 Combustion and Heating Air Fan ............................................................................................................201
2.2 Heat Exchanger.......................................................................................................................................202
2.3 Burner Insert with Combustion Tube.......................................................................................................202
2.4 Control Unit / Control Circuit Board.........................................................................................................202
2.5 Flame Sensor..........................................................................................................................................203
2.6 Glow Plug ................................................................................................................................................203
2.7 Temperature Limiter ................................................................................................................................203
2.8 Dosing Pump...........................................................................................................................................203
3.
Functional Description
3.1 Functional Description Air Top 2000 S .......................................................................................................301
3.1.1 Control Element ..........................................................................................................................301
3.1.2 Switch-On....................................................................................................................................301
3.1.3 Stabilization.................................................................................................................................301
3.1.4 Heating Operation.......................................................................................................................302
3.1.5 Control Operation........................................................................................................................302
3.1.6 Control Idle..................................................................................................................................302
3.1.7 Switch-Off....................................................................................................................................302
3.1.8 Switch-Off upon Failure...............................................................................................................302
4.
5.
Technical Data ...............................................................................................................................................401
Troubleshooting
5.1 General....................................................................................................................................................501
5.2 General Failure Symptoms......................................................................................................................501
5.3 Failure Symptoms during Operation........................................................................................................502
5.4 Error Code Output ......................................................................................................................................503
6.
Functional Tests
6.1 General....................................................................................................................................................601
6.2 Adjustments.............................................................................................................................................601
6.2.1 Adjustment of the CO2 Contents.................................................................................................601
6.3 Components Testing ...............................................................................................................................602
6.3.1 Glow Plug Resistance Test .........................................................................................................602
6.3.2 Flame Sensor Resistance Test...................................................................................................602
I
List of Contents
Air Top 2000 S
7.
Circuit Diagrams
7.1 General....................................................................................................................................................701
8.
Servicing
8.1 General....................................................................................................................................................801
8.2 Work on the Air Heater............................................................................................................................801
8.3 Work on the Vehicle ................................................................................................................................801
8.4 Air Heater Test Run.................................................................................................................................801
8.5 Servicing..................................................................................................................................................801
8.6 Visual Inspections and Installation Regulations ......................................................................................801
8.6.1 Heating Air System......................................................................................................................801
8.6.2 Fuel Supply .................................................................................................................................802
8.6.3 Dosing Pump...............................................................................................................................804
8.6.4 Fuel Filter ....................................................................................................................................804
8.6.5 Combustion Air Supply................................................................................................................805
8.6.6 Exhaust Line ...............................................................................................................................805
8.6.7 Combustion Air Intake and Exhaust Lines ..................................................................................805
8.6.8 Electrical Connections.................................................................................................................806
8.7 Removal and Installation .........................................................................................................................808
8.7.1 Air Heater, Removal and Installation...........................................................................................808
8.8 Start-Up...................................................................................................................................................808
Repair
9.
9.1 General....................................................................................................................................................901
9.1.1 Work on Components after Disassembly....................................................................................901
9.1.2 Incorporation of Modifications .....................................................................................................901
9.2 Disassembly and Assembly.....................................................................................................................902
9.2.1 Removal of Housing Components/Covers..................................................................................902
9.2.2 Replacement of Control Unit.......................................................................................................903
9.2.3 Replacement of Temperature Limiter..........................................................................................903
9.2.4 Replacement of Combustion Air Fan ..........................................................................................905
9.2.5 Replacement of Flame Sensor....................................................................................................907
9.2.6 Replacement of Glow Plug..........................................................................................................907
9.2.7 Replacement of Burner Insert, Combustion Tube, and Heat Exchanger....................................910
10. Packaging/Storage and Shipping
10.1 General..................................................................................................................................................1001
II
Air Top 2000 S
List of Figures
List of Figures
501
502
General Failure Symptoms .............................................................................................................................501
Failure Symptoms during Operation ...............................................................................................................502
601
Adjustment of CO2 Contents ..........................................................................................................................601
701
702
703
704
Terminal Pin Assignment, Air Top 2000 S.......................................................................................................701
Circuit Diagram Automatic Control Air Top 2000 S, 12V/24V with Control D i a l ............................................702
Circuit Diagram Automatic Control Air Top 2000 S, 12V/24V with Combination Timer ..................................703
Circuit Diagram Automatic Control Air Top 2000 S,
12V/24V with Control Dial and Standard Timer ..............................................................................................704
705
Connection Diagram, Air Top 2000 S with Combination Timer.....................................................................705
801
802
803
804
805
806
807
808
809
810
811
812
813
Fuel Supply.....................................................................................................................................................802
Webasto Fuel Tank Tap .................................................................................................................................803
Fuel Tapping from Plastic Tank (tapping via fuel drain plug)..........................................................................803
Fuel Tapping from Plastic Tank (tapping via fitting plate)...............................................................................803
Pipe/Hose Connection....................................................................................................................................804
Dosing Pump, Installation Position and Attachment .......................................................................................804
Fuel Filter........................................................................................................................................................804
Exhaust Muffler, Direction of Flow..................................................................................................................805
Exhaust Pipe Outlet, Installation Position .......................................................................................................805
Weather Resistant Fuse Holder........................................................................................................................806
Control Dial...................................................................................................................................................806
Pulling the Plug...............................................................................................................................................806
Example of an Installation...............................................................................................................................807
901
902
903
904
905
906
Removal of Housing Components/Covers......................................................................................................902
Replacement of Control Unit and Temperature Limiter...................................................................................904
Replacement of Combustion Air Fan (Disassembly)......................................................................................905
Replacement of Combustion Air Fan (Assembly............................................................................................906
Disassembly of Heat Exchanger (Sheet 1 of 2)..........................................................................................908
Disassembly of Heat Exchanger (Sheet 2 of 2)..........................................................................................909
III
List of Figures
Air Top 2000 S
IV
Air Top 2000 S
1. Introduction
1 Introduction
1.4 Safety Information and Regulations
The general safety regulations for the prevention of acci-
dents and the relevant operating safety instructions have
to be observed at all times."General Safety Regulations"
beyond the scope of these regulations are detailed in the
following.The specific safety regulations applicable to
this manual are highlighted in the individual chapters by
Warnings, Cautions, and Notes.
1.1 Scope and Purpose
This repair shop manual is intended to support famil-
iarized personnel in the repair of the Air Top 2000 S.
1.4.1 General Safety Notes
1.1.1 Use of Air Heaters
Within the scope of the StVZO (Road Licensing Regula-
tions of the Federal Republic of Germany) “Design
General Approvals”, laid down by the Federal Office for
Motor Traffic, exist for the Air Top 2000 S with the
following official marks of conformity:
The air heater Air Top 2000 S is used to
- heat the cabin
- defrost the windscreens.
They are not cleared for heating a transportation com-
partment for dangerous goods.
-S 324 (Diesel)
-S 325 (Gasoline)
The heaters operate independent from the vehicle en-
gine and are connected to the fuel tank and to the electri-
cal system of the vehicle. Their use is possible in
vehicles with water- or air-cooled engines.
The installation of the heater is to be performed in ac-
cordance with the installation instructions and must be
checked in case of
a) the vehicle type inspection in accordance with
§ 20 StVZO
b) the individual inspection in accordance with
§ 21 StVZO or
1.2 Meaning of Warnings, Cautions
and Notes
c) the examination in accordance with § 19 StVZO
performed by an officially authorised expert or exam-
iner for road traffic, a vehicle inspector or a public
servant as per section 7.4 a of Annex VIII to the
StVZO.
In the event of c) the installation must be certified on the
acceptance certificate included in the copy of the
“General Operating License” giving details about
WARNINGS, CAUTIONS, and NOTES in this manual
have the following meaning:
WARNING
This heading is used to highlight that non-compliance
with instructions or procedures may cause injuries or
lethal accidents to personnel.
-
-
-
manufacturer
type of vehicle , and
vehicle identification number.
CAUTION
This heading is used to highlight that non-compliance
with instructions or procedures may cause damage to
equipment.
This validates the “Design General Approval”.
The acceptance certificate must be kept with the
vehicle.
NOTE
The year of first operation must be permanently
marked on the identification label.
This heading is used to highlight and draw specific atten-
tion to information.
The heaters are cleared for heating the passenger and
driver cabins but not for heating compartments intended
for the transportation of dangerous goods.
1.3 Additional Documentation to be used
This workshop manual contains all information and pro-
cedures necessary for the repair of the Air Top 2000 S.
The use of additional documentation is normally not
necessary.
Operating instructions/installation instructions and the
vehicle specific installation proposal may be used as
complementary information as necessary.
101
1 Introduction
Air Top 2000 S
The heater must not be installed in the passenger or
driver compartments of busses. Should the heater never-
theless be installed in such a compartment, the installa-
tion box must be sealed tight against the vehicle interior.
There must be sufficient ventilation of the installation box
from the exterior in order not to exceed a maximum tem-
perature of 40 °C in the installation box.
Heating Air System
Heating air intake openings must be arranged so that
under normal operating conditions exhaust fumes of the
vehicle engine or air heater are not likely to be expected.
Extracting combustion air from the vehicle interior is not
permissible.
At filling stations and fuel depots the heater must be
switched off as there is a potential danger of explo-
sion.
Combustion Air Line
The combustion air required must be taken from the
exterior.
Within rooms accommodating persons, the combustion
air lines must not have more than four disconnects and a
splash-water protected exterior wall feedthrough. The
disconnects must be sealed in a way not to exceed a
leak rate of 200 l/h at an overpressure of 0.5 mbar.
The line including feedthrough, disconnects, material
and specific type must be described in the installation
instructions.
Where flammable fumes or dust may build up (e.g.
in the vicinity of fuel, coal, wood, cereal depots, or
similar installations) the heater must be switched off
to prevent explosions.
Due to the danger of poisoning and suffocation the
heater must not be operated in enclosed areas such as
garages or workshops without exhaust venting, not even
if the start-up is activated by the timer or telestart device.
The line must require tools for installation and removal,
must be protected against damage, and must be shock-
proof.
When removing the heater the gasket below must be re-
placed.
Exhaust Line
Heaters must be designed to discharge the exhaust to
The heat exchanger of the air heater remains service- the exterior.
able for a maximum of 10 years and must then be re-
placed with an original spare part by the manu-
facturer or by one of its authorized workshops.
The heater must then be provided with a label
Exhaust pipes must be routed so that exhaust fumes are
unlikely to penetrate into the vehicle’s interior.
The function of any parts of the vehicle essential for its
marked with the sales date and with the words “Orig- operation must not be impaired. Condensate or water
inal Spare”.
penetrated must not be able to accumulate in the
exhaust line.
Drain holes are permissible; these must drain the fluid to
the exterior via lines sealed against the vehicle interior.
Should exhaust pipes be routed through rooms
accommodating persons, these pipes shall also be
renewed after 10 years.
Installations not legally authorized will void the air
heater’s “Official Marks of Conformity” and thus the
vehicle’s permit of operation. The same applies for
repairs performed by unskilled personnel and repairs
with no original spare parts.
The exhaust line outlet is to be positioned to the top, to
the side, or in case of exhaust venting below the vehicle
floor, to the nearest possible location of the vehicle’s or
cockpit’s side or rear end. In compartments accommo-
dating persons, exhaust lines must not have more than
one disconnect and must have a splash-water protected
feedthrough in the exterior wall/floor. For water, that has
penetrated into the exhaust line, the connection of a
drain line with a metal-sealing joint is permissible. The
drain pipe must be routed sealed through the exterior
wall or the vehicle floor.The heat exchanger, the exhaust
line connected, as well as the possible drain pipe must
be sealed so that with an overpressure of double the
overpressure of the exhaust having the maximum per-
missible exhaust line length - at least however at an over-
pressure of 0.5 bar - a total leak rate of 30 l/h is not
exceeded.
1.5 Legal Provisions for Installation
For testing the heater in accordance with 19, 20, or 21
of the StVZO the following regulations are to be ob-
served in particular (§ 22 a StVZO):
Testing is performed upon presentation of the operating
and installation instructions of the manufacturer.
The year of the initial operation must be durably marked
on the heater identification plate by the installing person.
The line including feedthrough, disconnects, material
and specific type must be described in the installation
instructions.
The line must require tools for installation and removal,
must be protected against damage, and must be shock-
proof.
102
Air Top 2000 S
1 Introduction
Metal lines must be used. These may not heat to more
than 110 °C should there be the possibility of contact
within the room interior. Protective devices against con-
tact may be fitted.
Should exhaust pipes be routed through rooms accom-
modating persons, these pipes shall be renewed after 10
years using genuine spare parts.
Combustion Air Inlet and Exhaust Outlet
During installations these ports for combustion air entry
and exhaust fume exit must be of such type, that a ball
with a diameter of 16 mm cannot be inserted. Electrical
lines, switch gear and control gear of the heater must be
located in the vehicle so that their proper function cannot
be impaired under normal operating conditions.
For the routing of fuel lines and the installation of addi-
tional fuel tanks §§ 45 and 46 of the StVZO are to be
adhered to.
The most important regulations are: Fuel lines are to be
designed in such a way that they remain unaffected by
torsional stresses in the vehicle, engine movement and
the like. They must be protected against mechanical
damage.
Fuel-carrying parts are to be protected against ex-
cessive heat and are to be arranged so that any dripping
or evaporating fuel can neither accumulate nor be ig-
nited by hot components or electrical equipment.
In busses, fuel lines and fuel tanks may be located
neither in the passenger area nor in the driver’s compart-
ment. In these type of vehicles the fuel tanks must be lo-
cated such that they do not pose a direct hazard to the
exits in the event of a fire. Fuel supply must not be by
means of gravity or pressurization of the fuel tank.
Installation Rules for Webasto Fuel Tanks for the
Fuel Supply of Heaters in Vehicles
In busses the installation is not permitted in the pas-
senger or driver compartment.
The fuel fill neck must in no vehicle be located within any
of these compartments.
Fuel containers for gasoline fuel must not be located
immediately behind the front panelling of the vehicle.
They must be sparate from the engine so that even in
case of an accident the inflammation of fuel is unlikely to
be expected. This does not apply for towing vehicles
with an open cockpit.
The operational state of the heater, i.e. an indication “on”
or “off”, must be easily and clearly visible.
103
2 General Description
2. General Description
Air Top 2000 S
A malfunction of the Air Top 2000 S is indicated by an
error code displayed on the combination or standard
timer. When equipped with the standard control dial,
the operating indicator flashes. In addition a heater check
out may be performed using a personal computer (refer
to operating instructions PC air heater diagnosis).
The air heater Air Top 2000 S operates under the
evaporator principle and basically consists of:
- combustion and heating air fan
- heat exchanger
- burner insert with combustion tube
- control unit
Air Heater Air Top 2000 S
(covers removed)
Air Heater Air Top 2000 S
2.1 Combustion and Heating Air Fan
The combustion and heating air fan delivers the air re-
quired for combustion from the combustion air inlet to
the burner insert. By means of the fan the heating air is
also delivered to the hot air outlet.
For control and monitoring a
- control unit/control circuit board
- flame sensor
- glow plug
- temperature limiter
- temperature sensor
are located within the unit.
All Air Top 2000 S heaters may be controlled
by means of an optional external temperature sensor.
Fuel supply is provided externally by a fuel dosing pump.
Combustion and Heating Air Fan
201
Air Top 2000 S
2 General Description
2.2 Heat Exchanger
2.4 Control Unit / Control Circuit Board
The heat exchanger dissipates the heat provided by
combustion to the air delivered by the combustion and
heating air fan.
The control unit/control circuit board is the central con-
trolling unit for functional sequencing and monitoring of
the combustion operation. A temperature sensor located
on the control unit is used for temperature control. All
heaters may have the temperature sensor replaced
with an external temperature sensor. The combustion
and heating air fan may be set by means of a poten-
tiometer.
A malfunction in the Air Top 2000 S is indicated by an
error code displayed on the combination or standard
timer. When equipped with a standard control dial
the operating indicator flashes. In addition a heater check
out may be performed using a personal computer (refer
to operating instructions PC air heater diagnosis).
Heat Exchanger
Potentiometer
2.3 Burner Insert with Combustion Tube
Within the burner insert fuel is distributed in the combus-
tion tube across the burner cross-section. In the combus-
tion tube the combustion of the fuel/air mixture takes
place heating up the heat exchanger.
Temperature
Sensor
Combustion
Tube
Control Unit - Air Top 2000 S
Burner
Insert
Fuel
1 mm
Diesel
2 mm
202
2 General Description
Air Top 2000 S
2.5 Flame Sensor
2.7 Temperature Limiter
The flame sensor is a low-Ohm PTC resistor changing
its resistance dependent on its heating by the flame.
The signals are routed to the control unit for processing.
The flame sensor monitors the flame operating condition
over the complete duration of heater operation.
The temperature limiter protects the air heater against
excessive operating temperatures. Overheat protection
is activated at a temperature higher than 150 °C to inter-
rupt the electrical circuit of the dosing pump and switch
off the heater with run-down operation.
After cooling down the electrical circuit is restored.
The air heater may be switched on again (see 3.1.8).
Flame Sensor
Temperature Limiter
2.6 Glow Plug
The glow plug ignites the fuel/air mixture at the start of
the air heater operation. The glow plug is acting as an
electrical resistor and is located in the burner insert
opposed to the flame side.
2.8 Dosing Pump
The dosing pump is a combined supply, dosing and shut-
off system for the fuel supply of the heater out of the
vehicle’s fuel tank.
Glow Plug
Dosing Pump DP 2 for Gasoline and Diesel
operated Heaters
Dosing Pump DP 30 for Diesel operated Heaters
203
Air Top 2000 S
3 Functional Description
3.
Functional Description
Should no proper combustion develop within 120 sec-
onds (for fuel-operated within 115 seconds) the combus-
tion and heating air fan speed is increased to full load for
approx. 30 seconds (15 seconds for fuel-operated
heaters) with the glow plug on and the dosing pump off
(no fuel delivery) with a subsequent automatic restart.
3.1 Functional Description Air Top 2000 S
3.1.1 Control Element
The control element is used to switch the air heater on
and off, set the desired room temperature (air intake tem-
perature between 10 °C and 45 °C), and to unlock a
failure interrupt condition.
Should the no-combustion-condition persist, after an-
other 80 seconds (for fuel operated heaters after approx.
85 seconds) there will be a switch-off by error lockout
(see 3.1.8) with a run-down of the combustion and heat-
ing air fan lasting 120 seconds at 2/3 of its max. speed.
The green LED indication is used to indicate the opera-
ting condition (LED permanently on) and an overheat
condition (LED flashes).
2. Start (automatic restart)
Fan speed is again reduced to approx. 30% (for fuel
operated heaters to approx. 50%) and fuel is delivered.
During the next 20 seconds fan speed is increased to ap-
prox. 60% (for fuel-operated heaters to approx. 75%) of
full speed. As soon as a flame is detected within the next
55 seconds, combustion will be stabilized. Should there
be no flame condition after a total fuel delivery period of
180 seconds, fuel delivery will be stopped and the glow
plug deactivated. The combustion air fan continues full
load operation for another 120 seconds (run-down) and
the heater enters the error lockout condition.
3.1.2 Switch-On
The control element is set to the desired room tempera-
ture. When switching the air heater on, the operating indi-
cator is illuminated and the glow plug is activated
(cycled). The motor of the combustion and heating air
fan starts high-speed operation for 1 second (break-
away moment) and is then under slow-down control to
approx. 30% (Diesel) or 50% (fuel) of full speed.
NOTE
Should the temperature of the intake air be above the se-
lected, rated temperature, only the motor of the combus-
tion and heating air fan will operate (control idle). Start
operation will be initiated with a heating air temperature
below the rated temperature.
3.1.3 Stabilization
Diesel Operated Heaters
With the glow plug activated the operating speed of the
combustion and heating air fan is increased. After an-
other 20 seconds the speed of the combustion and heat-
ing air fan is continuously increased within 17 seconds
to full load for full heat.
The flame sensor function is checked. If the flame sen-
sor at this time already signals “flame”, there will be a
120 second run-down and an error lockout of the control
unit. A malfunction of any other component monitored
causes an error lockout without run-down.
NOTE
This operating condition is omitted if the set temperature
(control idle) has already been achieved once.
The glow plug is deactivated and heating operation com-
mences. A flame-out during speed up control causes a
restart, 5 restarts an error lockout of the heater.
After approx. 20 seconds (for fuel operated heaters after
approx. 15 seconds) the fuel dosing pump is activated.
After another 25 seconds the speed of the combustion
and heating air fan is continuously increased to a higher
rate and combustion begins. As soon as a flame is
detected, combustion will be stabilized (see 3.1.3).
Fuel Operated Heaters
With the glow plug activated the operating speed of the
combustion and heating air fan is continuously increased
within 4 seconds to full load for full heat. This operating
condition will be omitted if the start occurs after a control
idle period.
The glow plug is deactivated and heating operation com-
mences. A flame-out during speed up control causes a
restart, 5 restarts an error lockout of the heater.
Should no normal combustion be achieved within 120
seconds (for fuel operated heaters after approx. 115
seconds), the speed of the combustion and heating air
fan is increased for approx. 30 sec and there will be an
automatic repeat start with the glow plug activated and
fuel dosing pump deactivated (no fuel supply).
301
3 Functional Description
Air Top 2000 S
3.1.4 Heating Operation
3.1.7 Switch-Off
During operation the combustion exhaust gasses flow
through the heat exchanger charging its walls with com-
bustion heat, which in turn is taken up by the heating air
delivered by the heating air fan to be routed to the ve-
hicle interior.
Switching the heater off extinguishes the operation indi-
cation of the control element.
If no fuel has been delivered or if the air heater is in con-
trol idle, the air heater is deactivated immediately
without run-down.
The temperature of the heating air sucked in is
measured by means of a temperature sensor fitted to
the air intake side of the air heater or by means of an ex-
ternally located temperature sensor.
A temperature below the one set with the control ele-
ment increases the heater performance up to maximum
heat. In order to extend the burner idle period of Diesel
operated heaters during permanent operation with a
heating performance in excess of 1.1 kW, the fuel dos-
ing pump delivery rate is reduced every 15 minutes for
20 seconds.
If fuel supply has commenced it will be immediately
stopped at switch-off. Fan speed remains constant and
then decreases within 30 seconds to approx. 60% of full
speed. After this or with the flame sensor detecting “no
flame”, fan speed rises to maximum speed for 60 sec-
onds and run down for 120 seconds is initiated. Run-
down is at approx. 60% of full speed and is deactivated
automatically.
NOTE
Re-activation of the heater during run-down is permitted.
Run-down will be completed first with a subsequent re-
start.
A heating performance less than 1.1 kW causes the fuel
delivery to the dosing pump to be interrupted every 30
minutes for 4 seconds. Additionaly heating operation is
briefly suspended every 9 hours like in control idle. For
Diesel-operated heaters this is only applicable, if at this
time heating performance is less than 1.1 kW.
3.1.8 Switch-off upon Failure
The control unit recognizes failures of individual air
heater components and malfunctions in the start se-
quence and in normal operation.
3.1.5 Control Operation
During control operation fan speed and dosing pump
rate of delivery are subject to heating performance.
The glow plug is deactivated.
The air heater is deactivated and enters the error lock
out mode under the following conditions:
flame sensor open or short circuit
temperature sensor open or short circuit
glow plug open or short circuit
fan motor open or short circuit or fan speed wrong
dosing pump open or short circuit
3.1.6 Control Idle
After reaching the temperature set with the control ele-
ment, heating performance is controlled to decrease.
The speed of the combustion and heating air fan slows
down and the fuel delivery rate to the dosing pump is re-
duced. When exceeding the air intake temperature set
with the control element during minimum heating perfor-
mance, the dosing pump is deactivated after 5 seconds
and combustion terminates.
Fan speed remains constant for 35 seconds and is then
increased to approx. 60% of full speed for cooling the
heater down. the fan then continues to operate at ap-
prox. 30% of full speed until temperature is below the
temperature set with the control element. If temperature
falls below the one set with the control element, the
heater will restart (without break away).
overheating
low voltage below 10 Volt or high voltage above
15 Volt in excess of 20 seconds for 12 Volt heaters
low voltage below 20 Volt or high voltage above
30 Volt in excess of 20 seconds for 24 Volt heaters
A switch-off like in “switch-off” will be performed.
In case of overheating there will be no fuel supply. After
run-down the control unit is in the error lockout mode.
The operation indication outputs a flash code.
For error unlock the air heater has to be switched off
momentarily (at least 2 seconds) before switching on.
NOTE
New settings on the control element are executed by the
control unit/heater with a time delay.
302
Air Top 2000 S
4 Technical Data
Fuel for Air Top 2000 S B (gasoline):
4.
Technical Data
The fuel specified by the manufacturer must be used.
As long as no threshold values are given, the following
technical data are understood to include tolerances of
10% usual for heaters at an ambient temperature of
+20 °C and at nominal voltage and conditions.
Fuel for Air Top 2000 S D (diesel/PME):
The diesel fuel specified by the vehicle manufacturer
must be used.
We know of no negative influences due to additives.
Electrical Components:
If fuel is extracted from the vehicle’s tank, follow the
additive instructions issued by the vehicle manufacturer.
Control unit, combustion air fan, dosing pump, timer,
glow plug and control dial are for 12 or 24 Volts
operation.
If you change to low-temperature fuel, the heater must
be operated for approx. 15 minutes so that the fuel
system is filled with the new fuel.
The components temperature limiter and flame detector
are independent of voltage.
The Air Top 2000 S D heater is also licensed for use with
PME (bio-diesel), which complies with ASTM D6751 and
DIN EN 14214.
Air Heater
Operation
AT 2000 S B
~ S 325
AT 2000 S D
~ S 324
Mark of conformity
Heater type
Air heater with evaporator burner
Heat flow
Control range
Control range
1.1 – 2.0 kW
Gasoline
0.9 – 2.0 kW
Diesel/Fuel oil (EL)
Type of fuel
0.1 .. 0.2 kg/h (0.16..0.27 l/h)
12 Volt
0.1 .. 0.21 kg/h (0.12 .. 0.24 l/h)
Fuel consumption
Nominal voltage
Operation voltage
12 Volt
24 Volt
10 … 15 Volt
10 … 15 Volt
20 … 30 Volt
Rated power consumption Control range
Permitted ambient temp.:
9 ...22 W
-40 ° … +40 °C
-40 ° … +85 °C
-40 ° … +20 °C
-40 ° … +85 °C
-40 ° … +75 °C
-40 ° … +85 °C
- operation
- storage
Heater:
- operation
- storage
Dosing pump:
Control element:
- operation
- storage
Permitted combustion air
intake temperature
-40 ... +20 °C
Setting range for
+10 ... +45 °C
Control range
Max.
indoor temperature
Volume flow of heating air
against 0.5 bar
3
70 m /h
CO2 in exhaust
(perm. functional range)
9.5 … 10.5
9.5 … 12.0
Max.
Dimensions air heater
Weight, heater
Length 311 2 mm
Width 120 1 mm
Height 121 1 mm
2.6 kg
401
5 Troubleshooting
5. Troubleshooting
Air Top 2000 S
CAUTION
Troubleshooting is normally limited to the isolation of
defective components.
The following causes for trouble are not considered and
should always be checked for to exclude them as cause
for trouble:
5.1 General
A malfunction of the Air Top 2000 S is indicated by an
error code displayed on the combination or standard
timer. When equipped with a standard control dial
the operating indicator flashes. In addition a heater check
out may be performed using a personal computer (refer
to operating instructions PC air heater diagnosis).
corrosion on connector
loose contact on connector
wrong crimping on connector
corrosion on electrical wiring and fuses
corrosion on battery terminals
If individual components are checked, the control unit
electrical connections must be disconnected.
CAUTION
Troubleshooting requires profound knowledge about
structure and theory of operation of heater components
and may only be performed by skilled personnel.
After any correction of a failure a functional test has to
be performed in the vehicle.
In cases of doubt refer to Sections 2 or 3 for functional
interrelations.
5.2 General Failure Symptoms
The following table (Fig. 501) lists the possible failure
symptoms.
Failure Symptom
Probable Cause
Remedy
Air heater switches
off automatically
No combustion after start or repeat
start
Switch off heater momentarily and
switch on once again
Flame extinguishes during
operation
Switch off heater momentarily and
switch on once again
Heater overheats
Check heat air ducting for
Operation indication flashes
obstructions, allow heater to cool
down, switch off heater momentarily
and switch on once again
Vehicle electrical
Charge battery
system voltage too low
Switch off heater momentarily and
switch on once again
Heater expels black fumes
Combustion air and/or
exhaust ducting blocked
Check combustion and exhaust
ducting for obstructions
Fig. 501 General Failure Symptoms
501
Air Top 2000 S
5 Troubleshooting
failure symptom listed, in emergencies, assistance by our
service technicians may be requested.
5.3 Failure Symptoms during Operation
The following table (Fig. 502) lists the possible failure
symptoms as they might occur during the functional
sequence of operation.
NOTE
Overheating and dosing pump failure are always indi-
cated additionally after run-down by the flashing LED of
the control dial.
In case of malfunction the failure is to be isolated and
removed using this table. It is important to accurately
identify the failure symptom.
In all cases of trouble also a defective control unit may
be the cause should all other components turn out to be
serviceable.
Should the failure symptom not be contained in this
table or the trouble not be detected under the specific
Possible Causes
Failure Symptom
shows after
....seconds
Wrong cabling, defective fuse
Fan or control unit defective or fan blocked
No start and no illumination
of LED on control element
immediately
No start but LED illuminates
Very low speed with no start
immediately
immediately
Control idle operation: wrong manual control (selected
temperature is below air intake temperature) or wrong
integration (excessive air intake temperature)
Glow plug or flame sensor short or open circuit or
control unit defective
Motor operates momentarily
and then stops
1
Fan motor obstructed, binding
Flame detection erroneous
Voltage to control unit too low
Stoppage without run-down
Run-down after
5
1
Run-down after
20
120
Cabling to dosing pump, pump itself or overheat
protection defective
Run-down after
and dosing pump does not cycle
Intermittent disconnect of connection to dosing pump
or to overheat protection
Run-down after
Run-down after
40 to 120
230
No flame: wrong fuel supply quantity, defective or slow
fan, coked burner (in particular pilot flame outlet bore),
combustion air/exhaust ducting obstructed or heat
exchanger coked, dosing pump seized
Overheating or
voltage too low or
Run-down
during combustion
operation
component error (flame sensor, glow plug,
overheat sensor, dosing pump, burner) or
no fuel supply or obstructed combustion air/exhaust
ducting
Fan motor failure or seizure
Stoppage without run-down
during combustion
operation
Flame-out by gas bubbles in fuel delivery or strong
wind against exhaust outlet or defective no-flame
detection
Interruption of dosing pump
cycling and max. speed for
30 sec with subsequent re-start
during combustion
operation
Fig. 502 Failure Symptoms during Operation
502
5 Troubleshooting
Air Top 2000 S
5.4 Error Code Output
When equipped with a combination or standard timer a
malfunction will cause an error code output to the dis-
play of the timer for indication.
NOTE
When equipped with a control dial, the error code
output is indicated by flashing of the operating indica-
tor/error code indication. The number of flash pulses
corresponds to the number indicated in the table below.
After a quick pulse train there will always be an error
code output.
Error code output on display of combination or
standard timer
F
F
F
F
F
F
F
F
01
02
03
04
05
06
07
08
No start (after 2 attempts)
Flame out (at least >5)
Voltage too low or too high
Premature flame detection
Flame sensor open or short circuit
Temperature sensor open or short circuit
Dosing pump open or short circuit
Fan motor open or short circuit or
wrong speed
F
F
09
10
Glow plug open or short circuit
Overheating
503
Air Top 2000 S
6 Functional Tests
CAUTION
6.
Functional Tests
Set potentiometer slowly; observe end positions.
Adjustment may be performed at any electrical system
voltage.
6.1 General
This section describes the on-vehicle and off-vehicle
testing of the air heater to check its proper operation.
Clockwise rotation increases the fan speed and de-
creases the CO2 contents. Counterclockwise rotation de-
creases the fan speed and increases the CO2 contents.
WARNING
The air heater shall not be operated in enclosed areas
like garages or workshops not provided with exhaust
venting facilities.
If the setting range is not sufficient (e.g. after replace-
ment of the combustion and heating air fan) the manufac-
turer’s setting may be cancelled according to the
procedure described in the following.
6.2 Adjustments
6.2.1.2 New Basic Setting
6.2.1 Adjustment of the CO Contents
2
CAUTION
The manufacturer’s setting cannot be restored.
6.2.1.1 General
1. Withdraw cover from upper shell according to 9.2.1.
2. Switch on air heater.
3. Rotate potentiometer two times and with no interrupt
through its complete setting range (e.g. max. - min.-
max.).
4. Adjust desired CO2 contents (Fig. 601).
5. Switch off air heater.
6. Install cover and secure.
The CO2 contents of the exhaust is adjusted with the
potentiometer on the control circuit board. The air heater
is preset by the manufacturer with respect to the com-
bustion and heating air fan fitted. After adjustment by the
manufacturer the potentiometer is in center position
(Fig. 601). After an inadvertent loss of this position it is
sufficient to restore its original position.
The manufacturer setting may be corrected by rotating
the potentiometer. A suitable tool like a small screw
driver (2.5 mm tip) is to be used.
CO2
+
–
Fig. 601 Adjustment of CO2 Contents
601
6 Functional Tests
Air Top 2000 S
6.3 Components Testing
CAUTION
During electrical testing always ensure that the control
unit and the component under test are electrically discon-
nected from each other.
6.3.1 Glow Plug Resistance Test
During electrical testing of the glow plug using a digital
multimeter, the following readings should be obtained:
Glow plug
Resistance at 25 °C: 0.324 ... 0.360 Ω 1.3 ... 1.44 Ω
Test current: < 5 mA < 5 mA
12 Volt (red)
24 Volt (green)
6.3.2 Flame Sensor Resistance Test
During electrical testing of the flame sensor using a digi-
tal multimeter, the following readings should be obtained:
Cold test:
Resistance at 25 °C:
Test current:
2.6 ... 3.4 Ω
< 5 mA
Hot test:
Resistance at 800 - 1000 °C:
12 ... 15 Ω
(ceramic rod red hot over a length of approx. 20 mm)
Test current: < 5 mA
602
Air Top 2000 S
7 Circuit Diagrams
7.
Circuit Diagrams
7.1 General
The air heater Air Top 2000 S may be operated
using the control dial (rated value transmitter/switch)
or with the control dial and a combination or
standard timer. The circuit diagrams (Figs. 702 to 704)
show the possible circuits 12 or 24 Volt with
control element
combination timer
control element and standard timer
Fig. 701 shows the terminal pin assignment.
X1
X2
X3
X4
X5
violet
black
brown
yellow
blue
X1
X2
X3
X4
X5
= Connection, Combustion and Heating Air Fan
= Connection, Dosing Pump
= Connection, Flame Sensor
= Connection, Glow Plug
= Connection, Temperature Limiter
Fig. 701 Terminal Pin Assignment, Air Top 2000 S
701
7 Circuit Diagrams
Air Top 2000 S
2
?
?
?
Item
A1
Nomenclature
Air Heater
Remark
Wire Gauges
Air Top 2000 S
< 7.5 m
7.5 - 15 m
A2
Control Unit
2
2
1.5 mm
0.75 mm
2
2
B1
Flame Sensor
1.0 mm
1.5 mm
2.5 mm
1.5 mm
2
2
2.5 mm
B2
Temperature Sensor
Temperature Limiter
Glow Plug
2
2
2
4.0 mm
2
B3
4.0 mm
6.0 mm
E
Wire Colours
F2
Fuse 24V 10A/12V 15A
LED green (in item S1)
Motor
Flat Fuse SAE J 1284
Operation indication
bl
blue
H1
M
br
ge
gn
gr
or
rt
sw
vi
ws
brown
yellow
green
grey
orange
red
black
violet
white
S1
Control Element
Connection 2-pole
Connection 8-pole
Connection 4-pole
Connection 2-pole
Connection 2-pole
Connection 6-pole
Connection 1-pole
Dosing Pump
Rated Value Setting Switch
of item A2
X1-X5
X6
of item A2
X7
of item S
X8
X9
of item A2
2
Connection X11/2 and X11/3
for TRS function only
X11
X12
Y1
of item A2
Diagnosis (K-wire)
Fig. 702 Circuit Diagram Automatic Control Air Top 2000 S, 12V/24V with Control Dial
702
Air Top 2000 S
7 Circuit Diagrams
1
2
?
?
?
Item
A1
A2
B1
B2
B3
E
Nomenclature
Air Heater
Remark
Wire Gauges
Air Top 2000 S
< 7.5 m
7.5 - 15 m
Control Unit
2
2
1.5 mm
0.75 mm
2
2
Flame Sensor
1.0 mm
1.5 mm
2.5 mm
1.5 mm
2
2
2.5 mm
Temperature Sensor
Temperature Limiter
Glow Plug
2
2
2
4.0 mm
2
4.0 mm
6.0 mm
Wire Colours
F2
H7
Fuse 24V 10A/12V 15A
LED red (in item P)
Flat Fuse SAE J 1284
bl
blue
Instant heat switch illumination,
standy indication,
operating indicator light
br
ge
gn
gr
or
rt
brown
yellow
green
grey
orange
red
H8
Heating symbol in display (in item P)
Operating indicator light,
overheat indication
sw
vi
ws
black
violet
white
H9
Light (in item P)
Motor
Symbol illumination
M
P1
Combination Timer (1531)
Switch
S3
Instant heating remote control
of item A2
with plus from terminal (15/75)
to connection 10:
permanent operation during
instant heating as long as
ignition on
1
X1-X5
X6
Connection 2-pole
Connection 8-pole
Connection 2-pole
Connection 2-pole
Connection 6-pole
Connection 1-pole
Connection 12-pole
Dosing Pump
of item A2
X8
X9
of item A2
without plus to connection 10:
heating time programmable as
required (10 min to 120 min),
default setting 120 min.
X11
X12
X13
Y1
of item A2
Diagnosis (K-wire)
of item P
Connection X11/2 and X11/3
for TRS function only
2
Fig. 703 Circuit Diagram Automatic Control Air Top 2000 S, 12V/24V with Combination Timer
703
7 Circuit Diagrams
Air Top 2000 S
1
2
?
?
?
Item
A1
A2
B1
B2
B3
E
Nomenclature
Air Heater
Remark
Wire Gauges
Air Top 2000 S
Control Unit
< 7.5 m
7.5 - 15 m
2
2
1.5 mm
0.75 mm
Flame Sensor
2
2
1.0 mm
1.5 mm
2.5 mm
1.5 mm
Temperature Sensor
Temperature Limiter
Glow Plug
2
2
2.5 mm
2
2
2
4.0 mm
2
4.0 mm
6.0 mm
F2
H7
Fuse 24V 10A/12V 15A
LED red (in item P)
Flat Fuse SAE J 1284
Wire Colours
Instant heat switch illumination,
standy indication,
operating indicator light
bl
blue
br
ge
gn
gr
or
rt
brown
yellow
green
grey
orange
red
H8
Heating symbol in display (in item P)
Operating indicator light,
overheat indication
H9
Light (in item P)
Motor
Symbol illumination
sw
vi
ws
black
violet
white
M
P2
Standard timer
Control Element
Switch
S1
Rated Value Setting Switch
Instant heating remote control
of item A2
with plus from terminal (15/75)
to connection 10:
permanent operation during
instant heating as long as
ignition on
1
S3
X1-X5
X6
Connection 2-pole
Connection 8-pole
Connection 4-pole
Connection 2-pole
Connection 6-pole
Connection 1-pole
Connection 12-pole
Dosing Pump
of item A2
X7
of item S1
without plus to connection 10:
heating time programmable as
required (10 min to 120 min),
default setting 120 min.
X8
X11
X12
X13
Y1
of item A2
Diagnosis (K-wire)
of item P
Connection X11/2 and X11/3
for TRS function only
2
Fig. 704 Circuit Diagram Automatic Control Air Top 2000 S,
12V/24V with Control Dial and Standard Timer
704
Air Top 2000 S
7 Circuit Diagrams
Combination Timer 1531
Black
Battery Positive
or Ignition Signal (10)
Grey
Lights (1)
(optional)
Red
Battery Positive (11)
1V2
2V4
Brown
Battery Negative (12, 4)
Adapter Harness
P/N 9008440A
1
4
7
2
5
8
3
6
9
12 11 10
Fig. 705 Connection Diagram, Air Top 2000 S with Combination Timer
705
7 Circuit Diagrams
Air Top 2000 S
706
Air Top 2000 S
8. Servicing
8 Servicing
For reasons of the air heater’s functional reliability per-
form the following servicing:
check heating air inlet and outlet for foreign matter
and contamination. (Contaminated or clogged heat-
ing air ducts may lead to overheating and thus
response of the temperature limiter).
Clean air heater exterior (prevent the ingress of
water).
8.1 General
This section describes the servicing procedures that
may be performed with the air heater installed.
8.2 Work on the Air Heater
Examine electrical connections for corrosion of con-
tacts and for security.
Check combustion air and exhaust ducts for damage
and obstructions.
Check fuel lines and fuel filter for leakage.
Replace fuel filter if installed.
Prior to performing any work it is mandatory to discon-
nect the vehicle battery main lead. As long as the air
heater is in operation or in run-down, the battery main
supply must not be disconnected due to the danger of
overheating resulting in a response of the overheat pro-
tection.
8.6 Visual Inspections and Installation
Regulations
When performing extensive repairs on the heater a com-
plete removal is advisable. When performing repairs re-
quiring a relocation of the installation position, the
relevant installation instructions and the vehicle-specific
installation proposal have to be observed.
8.6.1 Heating Air System
CAUTION
The integration of the air heater into the vehicle’s own air
system is not permitted due to the system’s high press-
ure and temperature.
8.3 Work on the Vehicle
CAUTION
Fitted in the air heater on the heating air intake side is a
temperature sensor, which operates the heater in the
relevant range of performance in conjunction with the
control dial dependent on the air intake temperature
and position of the rated value transmitter. Heating per-
formance is selected so that after quickly reaching the
preselected indoor temperature it is maintained at this
value. Air Top 2000 S heaters may be operated with an
external temperature sensor (see 9.1.2).
In the vicinity of the air heater a temperature of 85 °C
must not be exceeded under any circumstances (e.g.
during body paint work).
8.4 Air Heater Test Run
WARNING
The air heater must not be operated, not even with
timer, in enclosed areas like garages or workshops not
equipped with an exhaust venting facility.
Minimum inside diameter of the heating air duct is
55 mm. Standard diameter is 60 mm.
CAUTION
NOTE
Operation of the heater without the control unit cover is
not permitted and causes overheating.
For heating air ducting only materials may be used
which are temperature-proof to at least 130 °C.
8.5 Servicing
Maximum loss of pressure between suction and delivery
side of the heating air duct 1.0 mbar (10 mm water
column).
NOTE
In order to avoid the seizure of mechanical components,
the air heater should be operated every 4 weeks for at
least 20 minutes.
When exceeding this value the temperature limiter is
very likely to respond. The heating air hose is to be se-
cured at its joints.
The air heater does not require maintenance. It should
however be checked by Webasto-trained skilled person-
nel on regular intervals, the latest before the heating
season begins (point of time, when the heater is more
frequently in use due to weather conditions).
801
8 Servicing
Air Top 2000 S
8.6.2 Fuel Supply
The fuel is taken from the vehicle fuel tank or from a
separate fuel tank. The values for maximum pressure
at the fuel extraction point are shown in Fig. 801.
Permissible fuel inflow
height H
At maximum pressure in
fuel line
0.00 m (0.00 in.)
1.00 m (39.4 in.)
2.00 m (78.7 in.)
0.20 bar (2.9 PSI)
0.11 bar (1.6 PSI)
0.03 bar (0.44 PSI)
max. 3m (9.8 ft.)
I
2
Maximum fuel intake
height S
At maximum negative
pressure in fuel tank
iØ2mm
0.00 m (0.00 in.)
0.50 m (19.7 in.)
1.00 m (39.4 in.)
-0.10 bar (-1.45 PSI)
-0.06 bar (-0.87 PSI)
-0.02 bar (-0.29 PSI)
iØ2mm
H
S
I
1
iØ2mm
8.6.2.1 Fuel Tapping
I
2
Vehicles with a Diesel Engine
The fuel must be taken from the vehicle fuel tank or
from a separate tank (Figs. 802, 803 and 804). This
separate fuel pickup precludes any effect of pressure.
+
≤ 10 m (32.8 ft.)
I
I
I
I
1
1
2
1
≤ 1.2 m (3.9 ft.)
≤ 8.8 m (28.8 ft.)
I
2
Vehicles with an Injection Engine
When installing the heater in a vehicle with fuel injection
systems, it is important to establish whether the fuel
pump is located inside or outside the tank.
Fig. 801 Fuel Supply
If the fuel pump is located inside the tank, fuel can only
be extracted from the return line using a Webasto fuel
tee fitting in which case it must be ensured that the
return line continues almost to the bottom of the tank.
If this is not the case, a Webasto fuel standpipe
(see Figs. 802, 803 and 804) may be used.
If the fuel pump is installed outside the tank, the fuel
connection may also be made between the tank and
fuel pump, again using only the Webasto fuel tee fitting.
Vehicles with a Carburetor Engine
The fuel may only be extracted on cars using a special
Webasto fuel tee fitting as close to the tank as possible.
The connection may be made in either the supply or
return line, in which case the return line must lead
almost to the base of the tank. If this is not the case,
the return line may be extended.
The fuel tee must be fitted in such a way that any air or
gas bubbles are automatically discharged towards the
tank.
The fuel tee should not be located near the engine, as
gas bubbles may form in the lines on account of heat
radiated from the engine. This may cause problems
during combustion.
802
Air Top 2000 S
8 Servicing
Hole Pattern
Fuel Tank Tap
Gaskets
25 mm (1 in.)
Tank Fitting Plate
Fig. 802 Webasto Fuel Tank Tap
* Use fuel tank tap only on metal fuel tanks
Fig. 804 Fuel Tapping from Plastic Tank
(tapping via fitting plate)
NOTE
Plastic Tank
The fitting plate must be made of sheet metal!
8.6.2.2 Fuel Lines
Fuel lines may only be steel, copper, or plastic lines
made of unhardened, light and temperature stabilised
PA 11 or PA 12 ( e.g. Mecanyl RWTL) according to DIN
73378. As in most cases a permanently rising fuel line
routing cannot be ensured, the inner diameter must not
exceed a certain value. Starting from an inside diameter
of 4 mm, air or gas bubbles accumulate resulting in mal-
functions should the lines be descending or have sags.
The diameters specified in Fig. 801 will ensure that
bubbles do not form.
Gasket
A descending line routing from the dosing pump to the
heater should be avoided.
Loose fuel lines must be secured in order to avoid sagg-
ing. The installation must ensure protection against
stone impacts and undue temperatures (exhaust line).
The fuel line joints are to be secured against slipping
with hose clamps.
Fig. 803 Fuel Tapping from Plastic Tank
(tapping via fuel drain plug)
803
8 Servicing
Air Top 2000 S
Connection of 2 Pipes with Hose
8.6.3.1 Installation Location
The proper connection of fuel lines with hoses is shown
in Fig. 805.
It is advantageous to mount the dosing pump in a cool
location. The ambient temperature must never exceed
+20 °C during operation.
Correct
Dosing pump and fuel lines must not be installed in loca-
tions exposed to heat radiated by hot vehicle compo-
nents. A heat shield is to be provided as required.
Clamp
8.6.3.2 Installation and Attachment
The dosing pump is to be attached with anti-vibration
mounts. The installation location is limited according to
Fig. 806 to ensure sufficient self-venting capability. Due
to the danger of corrosion the plug connection between
dosing pump and dosing pump cable loom may only use
Webasto original parts.
Wrong
Bubble
Bubble
8.6.4 Fuel Filter
Fig. 805 Pipe/Hose Connection
Only a Webasto filter, P/N 50487171A, is allowed to be
used if the fuel is expected to be contaminated. Install
vertically if possible, however at most horizontally (check
flow direction).
8.6.3 Dosing Pump
The dosing pump is a combined delivery, dosing, and
shut-off system and is subject to certain installation crite-
ria (see Figs. 801 and 806).
0 - 90°
A
ø 5
Fig. 807 Fuel Filter
AT 2000 S. 12 Volt and 24 Volt - Gasoline and Diesel
0-90°
0-90°
0°
AT 2000 S D. 12 Volt and 24 Volt - Diesel DP 30
Installation Position only Horizontal
Fig. 806 Dosing Pump, Installation Position
and Attachment
804
Air Top 2000 S
8 Servicing
Both lines must be routed away from the heater in a de-
scending attitude. If this is not possible, a condensate
drain hole ø 4 mm must be provided at the lowest point.
8.6.5 Combustion Air Supply
Combustion air must under no circumstances be ex-
tracted from rooms with persons. The combustion air
inlet must not point towards the forward direction of mo-
tion. It must be located so that no clogging by contamina-
tion is to be expected.
Inner diameter of lines:
Combustion air line: 22 mm
Exhaust line:
22 mm
NOTE
NOTE
When exceeding an exhaust line length of 2 m, insulated
exhaust lines have to be used (below minimum dew
point).
For fuel operated heaters the combustion air tap must
be located in a possibly cool and splash water proof posi-
tion using a combustion air line.
Smallest bending radius: 50 mm
If the air heater is located in a closed installation box,
combustion air must be taken in from and the exhaust
routed to the exterior. The feedthroughs must not allow
exhaust fumes to enter the vehicle interior.
In order to ensure the angle of 90° 10°, an attachment
is required not further than 150 mm away measured
from the exhaust pipe end.
If a contamniated combustion air supply is expected, a
combustion air filter (Ident No. 21963A) can be fitted
(Air Top 2000 S D only).
8.6.6 Exhaust Line
Rigid pipes made of unalloyed or alloyed steel with a
minimum wall thickness of 1.0 mm have to be used as
exhaust line or flexible pipes made of alloyed steel only.
The exhaust pipe is secured to the air heater e.g. with a
clamp.
Exhaust exit direction
nearly vertical 90° 10°
The exhaust muffler is preferably mounted near the air
heater. The direction of flow is optional.
10
°
10
°
ø 6,5
Fig. 809 Exhaust Pipe Outlet, Installation Position
WARNING
Fig. 808 Exhaust Muffler, Direction of Flow
Any exhaust exit direction other than the one shown in
Fig. 809 may cause fires.
Operation of the air heater is also permitted without
muffler.
Sum of bends:
Combustion air line: max. 270°
Exhaust:
max. 270°
8.6.7 Combustion Air Intake and Exhaust Lines
In order to avoid damage to the dosing pump cable, no
exhaust line may be used for the elongation of the com-
bustion air intake line.
Length of the combustion air intake and exhaust line:
with muffler:
without muffler:
max. 2.0 m
max. 5.0 m
805
8 Servicing
Air Top 2000 S
8.6.8.3 Connection Control Dial
8.6.8 Electrical Connections
The cable loom is prefabricated to connect to the control
dial (rated value transmitter).
8.6.8.1 Connection Air Heater, Control Dial
For plug disconnection pull on terminal plug only
(Fig. 812).
By pulling on the cable loom the terminal plug is
secured (self-locking).
Electrical connection is according to Circuit Diagram
Automatic Control (see Section 7).
For connection of the cable loom the cover (see 9.2.1.1)
of the air heater has to be removed for connecting the
cable loom plug(s) to the control unit. Avoid touching the
control unit strip conductors.
Prior to first operation of the air heater the cover must be
fitted to avoid the loss of heated air (air heater overheat-
ing).
The cable feedthrough may be from left or right.
8.6.8.2 Connection of Power Supply
Fiber optic lens
(operation indicator)
Ideally from the vehicle’s central electrical system.
Fig. 811 Control Dial
An additional blade terminal fuse holder is to be
fitted to protect the heater and harness (supplied
with the heater). The fuse holder should be
installed as close as is practical to the power
source e.g. in the vehicle battery enclosure.
NOTE
The fiber optic lens must be in contact with the
rotary knob.
The fuse holder is constructed of weather resistant
components.
AT 2000 S
F = 15A (12V)
F = 10A (24V)
Fig. 810 Weather Resistant Fuse Holder
Fig. 812 Pulling the Plug
806
Air Top 2000 S
8 Servicing
Fig. 813 Example of an Installation
807
8 Servicing
Air Top 2000 S
8.7 Removal and Installation
8.8 Start-Up
CAUTION
After you have installed the heater, bleed the fuel supply
system carefully.
When the heater is installed it must not be dismantled.
NOTE
8.7.1 Air Heater, Removal and Installation
8.7.1.1 Removal
As a result of the low fuel consumption the heater must
be switched on several times to fill the fuel line.
Conduct a trial of the heater to check all the connections
for leaks and to ensure that they are secure. If the
heater suffers a fault during operation, the fault must be
located and remedied.
1. Disconnect battery terminal leads.
2. Withdraw cover from upper housing shell according
to 9.2.1.
3. Disconnect the wire harness plug from control unit.
4. Disconnect interior air ducts if present.
5. Disconnect cable to dosing pump at cable disconnect.
6. Disconnect fuel inlet on air heater.
7. Disconnect connections of combustion air intake and
exhaust outlet on air heater.
8. Remove four nuts and lock washers on air heater.
9. Remove air heater and discard gasket.
8.7.1.2 Installation
1. Locate air heater with new gasket in installation
position and secure with four nuts and lock washers
(use original Webasto nuts only).
2. Tighten nuts with 6 + 1 Nm.
3. Secure connection for fuel inlet on air heater.
4. Secure connections for combustion air inlet and ex-
haust outlet on air heater.
5. Route cable to dosing pump and connect to dosing
pump.
6. Connect wire harness to control unit.
7. Install cover and secure.
8. Reconnect battery terminal leads.
9. Install interior ducting if present.
10. Bleed fuel supply system (see 8.8).
808
Air Top 2000 S
9. Repair
9 Repair
9.1.2.1 Installation of an External Temperature
Sensor
General
9.1 General
The heater can control the required temperature
perfectly if its temperature sensor is exposed to the air of
the main area of the vehicle. In certain circumstances,
this is not always possible using the temperature sensor
integrated in the control unit due to the installation
circumstances (addition of fresh air). In this case proper
temperature control can be ensured using an external
temperature sensor fitted in the appropriate area.
This section describes the repairs that may be per-
formed on the air heater Air Top 2000 S after it has
been removed from the vehicle.
Any further disassembly will void the warranty.
For reassembly, only components of the proper spare
parts and kits are to be used.
9.1.1 Work on Components after Disassembly
Procedure
1. Select adequate installation location for external
temperature sensor.
CAUTION
All gaskets located between disassembled components
as well as the exhaust outlet seal must always be re-
placed and discarded.
IMPORTANT
Temperature sensor should not be in the direct
line of heated air flow or located in the vicinity of
heating sources (e.g. vehicle’s own heater).
The sensor is to be installed at medium height
in the vehicle interior on surfaces that are as
vertical as possible.
The installation location should not be exposed to
direct sun light.
Do not mount temperature sensor behind curtains or
the like.
9.1.1.1 Cleaning
All components disassembled must be cleaned with
cleaning spirit and subsequently dried with press-
urized air.
All sealing compound must be carefully removed
from components using a suitable tool.
9.1.1.2 Visual Inspection
2. Mount external temperature sensor and route cable
to control unit.
3. Connect connector X9 and install cover.
4. Perform test run and check control behaviour.
Examine all components for damages (cracks, defor-
mation, wear, etc.) and replace as necessary.
Examine connectors and wiring for corrosion, loose
contacts, wrong crimping, etc. and repair as necess-
ary.
Check terminals for corrosion and contacts for
security. Repair as required.
9.1.2 Incorporation of Modifications
NOTE
Control Unit
The continous design improvement of the heaters is in-
tended to optimise their serviceability avoiding failures or
malfunctions.
In general equipment in service may be retrofitted with
available modification kits. In the following that modifica-
tion which may be incorporated easily during maintenace:
X9
Cover
installation of an external temperature sensor for
optimising temperature control of the Air Top 2000 S
(see 9.1.2.1).
External
Temperature Sensor
Connector X9
901
9 Repair
Air Top 2000 S
9.2.1.3 Covers for Heating Air Inlet and Outlet
9.2 Disassembly and Assembly
Both covers (3 and 6, Fig. 901) can be released and
removed by pressing the four detents on top and bottom
using a suitable tool.
9.2.1 Removal of Housing Components/Covers
9.2.1.1 Cover for Electrical Connection
9.2.1.4 Upper Housing Shell
Dependent on the type of installation the cable loom
exits the air heater either on the left or right.
The cover (1, Fig. 901) may be levered off using a blunt
blade in the areas marked X .
NOTE
The covers for the heating air inlet and outlet must be
removed.
9.2.1.2 Grates for Heating Air Inlet and Outlet
The upper shell (2, Fig. 901) can be raised by pulling up.
9.2.1.5 Lower Housing Shell
The grates (5, Fig. 901) can be released from the
covers by twisting and pulling off forwards.
By gently pulling the lower shell (4, Fig. 901) on both
Y
sides in the areas
, you can release the fixing and
the shell can be taken off the motor casing.
1
2
3
5
X
X
1 Cover, Electrical Connection
2 Upper Housing Shell
3 Cover, Heating Air Outlet
4 Lower Housing Shell
5 Grates
6 Cover, Heating Air Inlet
6
4
Y
5
Y
Fig. 901 Removal of Housing Components/Covers
902
Air Top 2000 S
9 Repair
9.2.2 Replacement of Control Unit
9.2.2.1 Removal
9.2.3 Replacement of Temperature Limiter
9.2.3.1 Removal
1. Remove heater from vehicle (see 8.7.1.1).
2. Remove covers for heating air inlet and outlet
(6 and 3, Fig. 901) according to 9.2.1.3.
3. Remove upper housing shell according to 9.2.1.4.
4. Disconnect plug connection (blue) from terminal.
5. Remove screws (4, Fig. 902).
During removal avoid the build-up of static charge (i.e.
do not touch strip conductors).
1. Remove heater from vehicle (see 8.7.1.1).
2. Remove covers for heating air inlet and outlet
(6 and 3, Fig. 901) according to 9.2.1.3.
3. Remove upper housing shell according to 9.2.1.4.
4. Disconnect terminal connections (1, Fig. 902).
5. Remove screws (3) and remove control unit (2)
with bracket (6).
6. Remove temperature limiter (5).
7. Perform work on components after disassembly
(see 9.1.1).
9.2.3.2 Installation
6. Remove screw (7) to separate control unit (2)
from bracket (6) if necessary.
7. Perform work on components after disassembly
(see 9.1.1).
1. Place temperature limiter (5, Fig. 902) into
installation position and secure with screws (4).
Ensure limiter is properly seated.
2. Torque screws to 1.5 ± 0.15 Nm.
3. Connect plug connections (blue) to terminal.
4. Install on upper housing shell and fix in position.
5. Slide on covers for heating air inlet and outlet and fix
in position.
9.2.2.2 Installation
NOTE
6. Install heater (see 8.7.1.2).
During installation avoid the build-up of static charge (i.e.
do not touch strip conductors).
1. Place control unit (2, Fig. 902) in position on
bracket (6) and secure with screw (7).
2. Place control unit (2) with bracket (6) in installation
position and secure with screws (3).
Torque screws to 0.7 ± 0.07 Nm.
3. Connect plug connections to terminal (Fig. 701).
4. Install upper housing shell and fix in position.
5. Slide on covers for heating air inlet and outlet and fix
in position.
6. Install heater (see 8.7.1.2).
7. Check CO2 setting and if necessary, adjust (see 6.2)
903
9 Repair
Air Top 2000 S
1
3
4
5
X6
2
7
6
1
2
3
4
5
6
7
Plug Connections
Control Unit
Screw (2)
Screw (2)
Temperature Limiter
Bracket
Screw
Fig. 902 Replacement of Control Unit and Temperature Limiter
904
Air Top 2000 S
9 Repair
1
!
MAX.
2
1 Insulation
2 Seal
Fig. 903 Replacement of Combustion Air Fan (Disassembly)
9.2.4 Replacement of Combustion Air Fan
9.2.4.1 Removal
5. Remove insulation (1, Fig. 903)
6. Remove screws (1, Fig. 904).
1. Remove air heater (see 8.7.1.1).
2. Remove control unit (see 9.2.2.1).
3. Remove seal (2 Fig. 903) from lower housing shell
and discard.
7. Withdraw combustion air fan (3) and remove gasket
(2).
8. Perform work on components after disassembly (see
9.1.1).
4. Remove air heater from lower housing shell.
905
9 Repair
Air Top 2000 S
9.2.4.2 Installation
•
•
•
Loose wire strands of the mesh must be cut off
to prevent contact with the temperature sensor.
1. Ensure that sealing surfaces on combustion air fan
and on heat exchanger are not damaged.
2. Place new gasket (2, Fig. 904) onto flange of
combustion air fan (3).
3. Place combustion air fan into assembly position and
mount using screws (1). Torque screws (1) to 6 Nm.
Ensure a secure fit between the heat exchanger,
insulating mesh, and the upper housing.
An overly worn, damaged or flattened insulating
mesh must be replaced with a new mesh.
4. Place wire insulating mesh into position on the
heat exchanger (1, Fig. 903).
CAUTION
To ensure the proper function of the heater and to
prevent malfunctions of the temperature sensor,
the following must be observed when installing the
wire insulating mesh:
5. While slightly spreading the lower housing shell,
place over heat exchanger until guide slots
engage with pins on fan housing.
6. Fit new seal (2, Fig. 903) on heater mount base.
7. Install control unit (see 9.2.2.2).
8. Install upper housing shell, air inlet and air outlet.
9. Install air heater (see 8.7.1.2).
10. Check CO2 setting and adjust as required (see 6.2).
•
The wire insulating mesh must be installed as
shown in Fig. 903 to prevent unwanted contact
with the temperature sensor terminals.
1
2
3
Screw (5)
Gasket
Combustion Air Fan
1
2
Before assembly always
renew gasket.
3
Combustion air fan must not be
disassembled any further
Fig. 904 Replacement of Combustion Air Fan (Assembly)
906
Air Top 2000 S
9 Repair
CAUTION
9.2.5 Replacement of Flame Sensor
9.2.5.1 Removal
The glow plug has to be pulled out with utmost care and
must under no circumstances be twisted (danger of
breaking). After a long period of combustion operation
the glow plug may be caked by fuel deposits. In this
case allow penetrating oil to react long enough to free
glow plug for removal.
1. Remove air heater (see 8.7.1.1).
2. Remove control unit (see 9.2.2.1).
3. Remove combustion air fan (see 9.2.4.1).
4. Remove screws (3, Fig. 905) and spoiler (2) for
cable protection.
5. Push out cable grommet (10) towards inside.
6. Carefully bend up locking tab (4) and withdraw flame
sensor (1) from burner insert (5).
7. Loosen screw (13) and remove glow plug (11)
from burner insert.
8. Perform work on components after disassembly (see
9.1.1).
7. Remove flame sensor.
8. Perform work on components after disassembly
(see 9.1.1).
9.2.6.2 Installation
1. Insert new gasket (7, Fig. 905) into heat exchanger
and place combustion tube (6) in assembly position.
2. Ensure that starting air bore is not clogged. If required
clean with wire (approx. 1 mm ø) (see Detail A).
9.2.5.2 Installation
CAUTION
Route cable of flame sensor below fuel pipe.
CAUTION
During glow plug installation observe twist lock (see De-
tail B). That means that the glow has to be inserted so
that the contacts point towards the heat exchanger.
Otherwise there will be the danger of a short circuit.
1. Pass flame sensor (1, Fig. 905) below fuel pipe, feed
connector through opening and push in cable grom-
met (10).
2. Feed cable with protection sleeve through locking tab
and insert flame sensor (1) into burner insert (5).
3. Squeeze locking tab (4).
4. Secure burner insert (5) with four screws (3) and fit
spoiler (2) for cable protection.
5. Pull cable of flame sensor tight.
3. Feed glow plug (11) into burner insert (5) and arrange
cable protective sleeve in slot of burner insert.
CAUTION
When performing the following step ensure that glow
plug is inserted in burner insert fully against stop.
6. Torque all 4 screws (3) to 6 ± 0.6 Nm.
7. Mount combustion air fan (see 9.2.4.2).
8. Install control unit (see 9.2.2.2).
4. Secure glow plug (11) with screw (13). Torque screw
(13) to 0.5 Nm.
9. Install air heater (see 8.7.1.2).
5. Locate burner insert (5) in heat exchanger (8) observ-
ing that cable of flame sensor is positioned below
fuel pipe.
6. Feed connectors of glow plug and flame sensor
through openings and push in cable grommets (9
and 10).
9.2.6 Replacement of Glow Plug
9.2.6.1 Removal
1. Remove air heater (see 8.7.1.1).
2. Remove control unit (see 9.2.2.1).
3. Remove combustion air fan (see 9.2.4.1).
4. Push out cable grommets (9 and 10, Fig. 905)
towards inside.
CAUTION
When performing the following step ensure that there is
a tight fit between grommet (12) and heat exchanger (8).
5. Remove four screws (3) and spoiler (2).
6. Tilt and withdraw burner insert (5) carefully.
7. Secure burner insert (5) using screws (3) and attach
spoiler (2). Torque screws (3) to 4 Nm.
8. Mount combustion air fan (see 9.2.4.2).
9. Install control unit (see 9.2.2.2).
NOTE
Ensure that burner insert (5) has separated from burner
tube (6).
10. Install air heater (see 8.7.1.2).
907
9 Repair
Air Top 2000 S
8
7
9
6
10
11
5
4
3
1
2
3
4
5
6
7
8
9
Flame Sensor
Spoiler
Screw (4)
Locking Tab
Burner Insert
Combustion Tube
Gasket
Heat Exchanger
Cable Grommet
13
2
10 Cable Grommet
11 Glow Plug
12 Grommet
13 Screw
12
1
Fig. 905 Disassembly of Heat Exchanger (Sheet 1 of 2)
908
Air Top 2000 S
9 Repair
Detail A
Starting Air Bore
Detail B
Twist Lock
Fig. 906 Disassembly of Heat Exchanger (Sheet 2 of 2)
909
9 Repair
Air Top 2000 S
9.2.7 Replacement of Burner Insert,
Combustion Tube, and Heat Exchanger
CAUTION
If the heat exchanger is going to be replaced, the
temperature limiter must also be replaced.
9.2.7.1 Removal
1. Remove air heater (see 8.7.1.1).
2. Remove control unit (see 9.2.2.1).
3. Remove combustion air fan (see 9.2.4.1).
4. Remove flame sensor (see 9.2.5.1).
5. Remove glow plug (see 9.2.6.1).
CAUTION
When performing the following step ensure that fuel
connection is not bent.
6. Remove burner insert (5, Fig. 905).
7. Withdraw combustion tube (6) from heat exchanger
(8) and remove gasket.
8. Perform work on components after disassembly (see
9.1.1).
9.2.7.2 Installation
1. In case a new heat exchanger is fitted, secure
temperature limiter (5, Fig. 902) with screws (4).
Torque screws to 1.5 ± 0.15 Nm.
2. Fit new gasket (7, Fig. 905).
3. Bring combustion tube (6) in assembly position.
NOTE
The burner insert will be secured when installing flame
sensor and glow plug.
CAUTION
When performing the following step ensure that the fuel
connection is not bent.
4. Install glow plug (see 9.2.6.2).
5. Install flame sensor (see 9.2.5.2).
6. Mount combustion air fan (see 9.2.4.2).
7. Install control unit (see 9.2.2.2).
8. Install air heater (see 8.7.1.2).
910
Air Top 2000 S
10 Packaging/Storage and Shipping
10. Packaging/Storage and Shipping
10.1 General
When it is necessary to ship the heater and its components
to a Webasto repair center for inspection or repair, they
are to be cleaned and packaged so that they are protected
against damage during handling, transportation, and
storage.
In storage an ambient temperature of +85 °C and -40 °C
must not be exceeded.
06/2008
1001
Notes
Air Top 2000 S
WEBASTO PRODUCT N.A., INC.
15083 North Road
Fenton, MI 48430
Technical Assistance Hotline
USA:
Canada:
(800) 860-7866
(800) 667-8900
Org. 06/2008 Rev. N/A
P/N LIT9000557A
© 2008 Webasto Product N.A., Inc.
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