Stationary Heater, Basic Function - GF83.70-P-9900A

Model All (4xWD) 

Model All (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Ventilation mode 
  • Heating mode 
  • Ventilation/heating mode triggered after entering departure time 
  • Check 

General 

The stationary heater can also be used for vehicle interior heating or ventilation even when the vehicle has been switched off. The heater is the central component part of the stationary heater. It is connected to the engine's coolant circuit and it contains all the component parts required for heat generation, including the stationary heater control unit.

Function requirements 

• Stationary heater switched on
• Fuel level above coded value
• No overvoltage or undervoltage
• Vehicle interior and outside temperature determined

Function 

A fuel pump supplies the heater with the required fuel. The fuel is burnt in the combustion chamber and it heats up the coolant. A circulation pump routes the heated coolant through the coolant circuit. The blower provides ventilation for the vehicle interior.

The stationary heater is controlled using the stationary heater control unit. The heating mode request is issued however from the climate control, control system. This evaluates all variables and communicates with the stationary heater control unit.

In its basic setting, the maximum heating/ventilation duration is approx. 50 min. A change can be made to the basic setting using the diagnosis tester in 5-minute increments between 10 and 60 minutes.

The ventilation/heating mode can be triggered immediately or it can be preprogrammed by entering a departure time. The following control elements are available:

• Stationary heater button
• Multimedia system (for pre-programming only)
• Radio remote control (equipment specific)
• Remote telematics services (equipment specific)

Depending on the vehicle model involved, the stationary heater can also be switched on while driving (heater booster mode).

The function can be ended in the following ways:

• Automatically approx. 5 minutes after reaching the programmed departure time (if engine not started).
• Automatically, if the difference between the coolant temperature in the engine and the coolant temperature at the stationary heater outlet is less than approx. 5°C (when engine is started).
• Automatically if heater overheats.
• Automatically at undervoltage.
• Automatically if crash signal is recognized.
• Manually through stationary heater button, radio remote control or remote function of telematics services.

The stationary heater control unit continuously sends information on the operating status of the stationary heater to the radio remote control receiver. The information is stored there and it can be retrieved using the radio remote control transmitter. The information is only provided in response to a request from the radio remote control transmitter.

If, in the event of an accident, the SRS system sends a crash signal to the stationary heater control unit, the stationary heater control unit switches off the heater. This reduces the risk of fire.

Ventilation mode 

In the ventilation mode, the climate control, control system actuates the blower regulator. The blower regulator controls the blower motor speed.

Heating mode 

Depending on the equipment installed, the stationary heater control unit or the air conditioning control panel actuates the circulation pump directly.

During heating mode the circulation pump continuously circulates the coolant. The heater heats up the coolant.

As from a coolant temperature of approx. 50°C, the stationary heater control unit switches on the blower motor. The coolant dissipates the heat into the vehicle interior by way of the heat exchanger.

Ventilation/heating mode triggered after entering departure time 

The climate control system sends the inputted departure time, depending on the vehicle, to the instrument cluster control or to the electronic ignition lock control unit.

Roughly 60 minutes before the entered departure time, the instrument cluster control or the electronic ignition lock control unit requests the ventilation/heating duration required to reach the set specified temperature from the control system of the climate control. The climate control system then calculates the required ventilation/heating duration based on the outside temperature.

The climate control system sends the calculated ventilation/heating duration for calculating the switch-on time, depending on the vehicle, to the instrument cluster control or to the electronic ignition lock control unit. Once the switch-on time is reached, the instrument cluster control system or the electronic ignition lock control unit sends a switch-on request to the climate control system.

Check 

Before starting the heating mode, the stationary heater control unit checks the status of all components involved in the heating mode. If a fault is detected, the heating mode is not started. The ventilation mode is activated by the heater irrespective of the test result.

The heater runs a self-test to verify the detected faults. The status is updated by the result of the self-test. Depending on the result, the heater can start the heating mode again the next time an attempt is made to switch it on.

The stationary heater control unit checks the following components among others when starting and during the heating mode:

• Temperature sensor
• Thermal fuse
• Combustion air blower
• Glow plug/flame monitor unit
• Switchover valve
• Fuel pump (FP)

A defective switchover valve does not result in interruption of the heating mode or interruption of it starting because this component part is not relevant for safe operation of the stationary heater. It only leads to performance loss.

The air conditioning control panel activates the ventilation or heat function to match the requested and actual interior temperature.