Additional heater (diesel engines only)
Control of the additional heater on cars with manual climate control (MCC)
The climate control module (CCM) requests that the combustion preheater module (CPM) is started. The central electronic module (CEM) determines whether start is possible. The combustion preheater module (CPM) then receives a signal from the central electronic module (CEM) to start the heater.
Certain conditions must be met before the heater can start. These are:
- Outside temperature below +8 °C (at 12 °C the heater switches off)
- Engine running
- Quantity of fuel greater than 4 liters
- No diagnostic trouble codes (DTCs) that will prevent starting are stored in the central electronic module (CEM)
- The airbags have not deployed.
The heater makes three start attempts. If these fail a diagnostic trouble code (DTC) is stored in the central electronic module (CEM) and a warning message is displayed in the driver information module (DIM). If the conditions change the central electronic module (CEM) requests that the heater is stopped.
Control of the additional heater on cars with electronic climate control (ECC)
The additional heater is controlled by the ECC climate control system as required. In addition to the above conditions, the climate control module (CCM) also takes the outside temperature, engine coolant temperature (ECT) and the temperature selected into account before a request for the heater to start is made.