Design
Design
Additional heater (diesel engines only)
Control of the additional heater on cars with standard (STD) and manual climate control (MCC)
The climate control module sends a request to the combustion preheater module that the additional heater should start. The central electronic module determines whether start is possible. The combustion preheater module then receives a signal from the central electronic module to start the heater.
Certain conditions must be met before the heater can start. These are:
- Outside temperature less than +8 °C (The heater stops at 12 °C)
- Engine running
- Quantity of fuel greater than 4 liters
- No diagnostic trouble codes (DTCs) stored in the central electronic module that will prevent starting
- Airbag not deployed.
The heater makes three start attempts. If these fail a diagnostic trouble code (DTC) is stored in the central electronic module and a warning message is displayed in the combined instrument panel (driver information module). If the conditions change the central electronic module requests that the heater is stopped.
Control of the additional heater on cars with electronic climate control (ECC)
In cars with climate control the additional heater is activated when required. In addition to the above conditions, the climate control module 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.
Parking heater
The start time for the heater is always programmed by selecting the desired parking function using the ring on the control stalk and entering the desired time by turning the ring and pressing the "reset" button. Direct start can also be used to start the heater.
The climate control module is activated when the engine coolant temperature (ECT) is greater than +20 °C. The blower fan starts and distributes the air in the passenger compartment.
Certain conditions must be met before the heater can start. These are:
- Quantity of fuel greater than 4 liters
- No diagnostic trouble codes (DTCs) stored in the central electronic module that will prevent starting
- Airbag not deployed.
When the conditions are met, the heater glow plug is activated for 1 minute. If the voltage has dropped below 11.5 V, the climate control module is stopped. The heater and the climate control module are stopped if the voltage falls below 11.3 V. A message indicating low battery voltage is displayed in the combined instrument panel (driver information module). These voltage values apply even if the heater is operating normally.
To minimize the risk of the fuel pump for the heater failing due to lack of use, the central electronic module sends a signal every week to the combustion preheater module to activate the pump for approximately 1 second. This takes place when the ignition is switched off.