Component Tests and General Diagnostics

System Values For Auxiliary Heater

Auxiliary heater system
During auxiliary heater operation, the changeover valve isolates the auxiliary heater circuit from the engine cooling circuit. The circulating pump pumps coolant through the auxiliary heater circuit. Based on the temperatures in the heater circuit, the correct function of the system components can be derived. Select and check suspected components in the main menu.

Behavior 1: Target behavior
Heat exchanger temperature increases as auxiliary heater temperature increases. The engine coolant temperature remains constant (image 1).

Behavior 2: Changeover valve faulty
Heat exchanger temperature, auxiliary heater temperature and engine coolant temperature all increase (image 2).

Behavior 3: Faulty circulating pump
Auxiliary heater temperature increases. Heat exchanger temperature does not increase. Engine coolant temperature remains constant.