Information on unlocking the heating system (removing fault lockout)

If the auxiliary heating system is locked, the service function must reset the auxiliary heater fault lockout.

Information on locked auxiliary heating unit

Causes of a fault lockout can be:

• Undervoltage cutout
  
• Overheating protection function triggered
  
• Lack of fuel
  

If the unlocking of the auxiliary heating system is unsuccessful within the service function, it must be unlocked manually.

Procedure for manual unlocking:

To unlock the auxiliary heating system, it is important that the control module has been woken up. This can be done either using the diagnostic tester or by simple bus communication in the vehicle. If the bus is active and the voltage supply is interrupted for approx. 5 seconds (fuse removed) and reconnected, the auxiliary heating system is unlocked.

Information regarding disruption-free use of the auxiliary heating system:

• Avoid undervoltage; check the battery and alternator; explain the problem of short distance driving to the customer. In the case of undervoltage, it can also occur that the integrated automatic heating/air conditioning system (IHKA) does not send a start telegram to the auxiliary heating system and thus no independent heating is possible. Please always read out the IHKA fault memory and/or include it in the diagnosis of the independent heating.
  
• When the fuel tank is at reserve, auxiliary heating is not possible in any situation. There does not have to be a fault lockout.
  
• Smoking: the auxiliary heating system is a vaporizing burner, i.e. during short distance driving the burner receives a rich mixture a number of times and smoke can develop due to the design principle. The short combustion phases mean there is no burn-off.