Webasto Air Top 3500 Service Manual

Webasto Air Top 3500 Service Manual
Webasto Air Top 3500 Workshop Manual

This repair shop manual is intended to support familiarised personnel in the repair of the air heaters Air Top 3500, Air Top 3500 Volume Plus and Air Top 5000 of the Diesel type. This workshop manual contains all information and procedures necessary for the repair of air heaters Air Top 3500 and Air Top 5000. 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.

Use of the Webasto Air Heaters
The air heaters Air Top 3500 and Air Top 5000 are used to

  • heat the cabin
  • defrost the windscreens
  • heat the goods in transport

They are not cleared to be used for heating a compartment intended for the transportation of dangerous goods. The heaters work independently from the vehicle engine and are connected to the vehicle's fuel and electrical system. The use in vehicles with water or air cooled engine is possible.

 The heaters are cleared for heating the passenger and driver cabin, but not for heating a compartment intended for the transportation of dangerous goods. When using the heater in special vehicles (e.g. vehicles for the transportation of dangerous goods ADR) or in vehicles not subject to the Road Licensing Regulations (StVZO) (e.g. ships), the applicable partially regional regulations must be observed.

When installing the Air Top 3500 and Air Top 5000 in vehicles intended for the transportation of dangerous goods, the TRS 002 and TRS 003 (Technical Guidelines for Regulations concerning the transportation of dangerous goods on roads) must be met in addition to the StVZO (Road Traffic Licensing Regulations).

The heater must not be installed in the passenger or driver cabin of busses. Should the heater nevertheless be installed in such a compartment, the installation 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 temperature of 40 °C in the installation box. Excessive temperatures may cause malfunctions.

The heater must be inspected by an expert in time before the beginning of the heating season. Should the heater develop strong smoke emissions over extended periods of time, unusual combustion operating noise or smell of fuel, the heater must be made inoperative by removing the fuse and returned into service only after inspection by Webasto trained personnel. Claims for warranty may only be made providing evidence by the claimant that maintenance and safety regulations have been met.

The air heaters Air Top 3500 and Air Top 5000 working to the evaporator principle of operation basically consist of the:

  1. combustion and heating air fan
  2. heat exchanger
  3. burner
  4. combustion tube
  5. control unit

For control and monitoring the following components are located inside the air heater:

  • control unit
  • glow plug / flame sensor
  • analogue temperature limiter
  • temperature sensor

The heater may be controlled by means of an external temperature sensor instead of the internal temperature sensor. Fuel supply is provided by an external dosing pump. In case of a heater malfunction an error code is output to the display of the combination timer. When equipped with a control element, the operating indicator light will flash. The heater may be additionally checked using a personal computer (refer to operating instructions for PC heater fault diagnosis).

Webasto Air Top 3500 Analogue Temperature Limiter
The analogue temperature sensor protects the heater against undue high operating temperatures. For protection against overheating the temperature limiter responds at a heating air temperature higher than 150° C. The control unit disconnects the dosing pump circuit and deactivates the heater with a run-down. After cooling down the circuit is re-established. The heater may be reactivated by switching the heater off and on again using the control element.

Webasto Air Top 3500 Error Lockout
The control unit detects malfunctions of individual heater components and errors in the start sequence and in heater operation. The heater is switched off and enters error lockout under the following conditions:

  • control unit error
  • no start
  • flame-out
  • premature flame detection
  • temperature sensor open circuit or temperature sensor short circuit
  • glow plug/flame sensor open circuit or glow plug/flame sensor short circuit
  • fan motor open circuit or fan motor short circuit or fan motor wrong speed
  • dosing pump open circuit or dosing pump short circuit
  • temperature limiter open circuit or temperature sensor short circuit
  • overheating
  • voltage too low, less than 10 Volt or
  • voltage too high, more than 15 Volt for longer than 20 seconds (12 Volt heaters)
  • voltage too low, less than 20 Volt or
  • voltage too high, more than 30 Volt for longer than 20 seconds (24 Volt heaters)
  • control element open circuit

Switch off is identical as described in "Switch off". In case of overheating there will be no fuel delivery. After run-down the control unit will be in error lockout. The control element will display a flash code. For error lockout reset switch off heater (at least for 2 seconds) and switch on again.

Combustion Air Supply for Webasto Air Top 3500
The combustion air must not be taken in from rooms accommodating persons. The intake must not point in the direction of forward motion. The combustion air intake must be located so that clogging by contamination is not to be expected. The use of an air intake muffler or an equivalent air intake extension is necessary. If the heater is contained in an installation box, the combustion air must be taken in from and the exhaust vented to the exterior. The line feedthroughs must not allow exhaust fumes to enter the vehicle interior.


Leave a Reply

Your email address will not be published.Required fields are marked *