| Pos. | Spare part number | Name |
| 1 | - | Heater assembly |
| 2 | - | Electric additional heater |
Since diesel engines warm up more slowly, an electric booster heater may be installed to improve the efficiency of the heater. The electric booster heater heats the air coming out of the heater unit.
The electric additional heater is equipped with ceramic-coated thermistor elements and a micro-controller. The request for switching on the electric additional heater is generated in the automatic temperature control (ATC) module. This request is transmitted to the central junction box (CJB) via the medium-speed CAN bus. The CJB interprets this request and sends a PWM (pulse width modulation) signal to the micro-controller of the electric additional heater. The duration of the pulses emitted by the CJB is proportional to the required heating intensity.
The heating intensity requested by the ATC module depends on the following factors:
- Outside air temperature
- Engine Coolant Temperature (ECT)
- Heating request
NOTE: The electric booster heater also requires the blower motor to run at minimum speed to operate.
The power of the electric additional heater is limited to 1.25 kW. If the electrical load control is active, the efficiency of the electric additional heater is reduced.
NOTE: Vehicles equipped with electric booster heater and heated windshield use an upgraded 180 amp alternator. For additional information, refer to: Alternator - 2.2L Duratorq - Td4 (414-02 Alternator and Voltage Regulator, Description and Operation).
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