Auxiliary Cabin Heater: Description and Operation

GF83.75-P-2000GI Residual Engine Heat Utilization System, Function
- with CODE (580a) Automatic air conditioning

Function
The residual engine heat utilization system allows the vehicle to be heated even when the ignition is switched OFF. To this end the system uses the residual heat of the engine. The residual engine heat is dissipated to the coolant and routed through the heat exchanger with the aid of the heating water circulation pump. The air drawn in by the blower motor is routed around the heat exchanger, whereby it is then warmed up. The heated air is then routed over the air outlets into the passenger compartment. The residual engine heat utilization system can only be used when the ignition is switched OFF.

Once the Rest pushbutton ( [REST] ) on the AAC pushbutton control module (N22) has been pressed the following program sequence is run:
- Blending air flaps are automatically controlled
- Heating water circulation pump ON
- The blower's control voltage is limited to a maximum value of 5 Volt.

End of program
- Pressing the Rest pushbutton ( [REST] )
- Timeout of 30 minutes period (repeated operation possible)
- Protection against undervoltage at a battery voltage of less than 11 V (LED flashes)
- Ignition ON

During the residual engine heat utilization function no function keys are accepted apart from the Rest pushbutton ( [REST] ) and the set point adjusters.