GF83.70-P-0006T Stationary Heater (STH), Function
GF83.70-P-0006T Stationary Heater (STH), Function
- with CODE (228) Stationary heater
General information
Prior to starting a journey during the cold season the stationary heater (STH) ensures that:
^ the passenger compartment is preheated,
^ the windows are free of ice and condensation,
^ the engine is preheated.
The use of the stationary heater reduces:
^ the risk of an accident by providing excellent vision before starting out on a trip,
^ the mechanical wear to the automotive engine associated with a cold start,
^ fuel consumption and at the same time it also helps to preserve environmental resources by cutting down the pollutants in exhaust emissions when starting up a previously heated engine.
The stationary heater also contains the stationary ventilation function.
This provides for the following at high ambient temperatures and a high interior temperature due to intense solar radiation:
^ the interior is ventilated,
^ stored heat is reduced.
It is not possible to reduce the temperature to less than the outside temperature.
The main component is the STH heater unit (A6). The heater unit comprises all components necessary for generating and exchanging heat.
The heater unit is connected directly to the heater and coolant circuits for the automotive engine and utilizes them, together with its own circulation pump (M13), to transmit heat.
The STH fuel metering pump (Y23) provides the fuel supply for the heater unit.
To enable the interior to be heated up faster, the heater unit regulates the flow of coolant to match temperature between the small and large coolant circuit by way of the STH switchover valve (A6y1).
Possible activation modes
The heater mode or stationary ventilation can
^ be preprogrammed via the instrument cluster (A1) or
^ switched on using the STH radio remote control transmitter (A8/3) or
^ with the STH switch (N72s12)
In the instrument cluster up to three preselect times can be stored, of which only one can be activated. The multifunction display (A1p13) in the instrument cluster serves here as a display instrument.
Terminate heater mode or stationary ventilation
The functions are automatically terminated by the stationary heater itself or they can be manually canceled in advance using the stationary heater transmitter or the STH switch.
Switchover between stationary heater and stationary ventilation
The stationary heater can correct the heating or ventilation choice as often as required. Depending on the temperature conditions, it can also change between ventilation and heating.
Component test
Prior to starting the heating mode, the status of all involved components is queried and a self-test performed where required. The heating mode is not started in the event of a relevant fault. The stationary ventilation function however is always performed, irrespective of the result.
Engine start during heating mode
The stationary heater primarily heats up the vehicle interior. Heating of the engine coolant is secondary. If the engine is started during stationary heater operation, then the engine initially heats itself and then its starts to heat the interior, as soon as the coolant temperature in the automotive engine (large circuit) exceeds the temperature of the heat exchanger (small circuit).
Heater booster function when driving (with diesel engine)
If the engine heat emission is insufficient to heat the vehicle interior, the heater unit is automatically activated for heating. At a coolant temperature of 82 °C the heater booster function automatically switches off and if the temperature drops to 72 °C, it switches on again automatically insofar as the requested interior temperature requires heater booster operation.
Consumer shutoff:
To prevent the battery from being discharged, the state of charge in the on-board electrical system is continuously evaluated. If a specific voltage value is dropped below, any consumers that require large currents are switched off until the state of charge is again acceptable. This also applies for the stationary heater.
Safety shutoff in the event of crash
In the event of a crash signal, issued by the restraint systems control unit (N2/7), the heater unit is permanently switched off. The shutoff process can only be reset using STAR DIAGNOSIS.
Teach-in of the STH transmitter
Before initial startup the STH radio remote control receiver (A6/1) must undergo a "teach-in" of the STH transmitters allocated to it. To do so, the STH switch must be operated for approx. 20 s, until the red indicator lamp flashes on and off. After releasing the STH switch, the teach-in period window is opened for a max. of 5 s.
The STH receiver notes the first, valid transmission signal it receives as the signal from the STH transmitter allocated to it. Following this, it then closes the teach-in period window and it has to be opened again to teach in another STH transmitter. The STH receiver can store up to 3 STH transmitters. If an additional STH transmitter undergoes teach-in, then the STH transmitter that underwent teach-in first is deleted.
The teach-in window can also be opened using STAR DIAGNOSIS. The various opening times can only be configured using STAR DIAGNOSIS, similarly the number of STH transmitters that have undergone teach-in are read out.
