GF83.70-P-0006GZ Stationary Heater (STH), Function
GF83.70-P-0006GZ Stationary Heater (STH), Function
General information
Prior to starting a journey during the cold season the stationary heater (STH) ensures that:
^ the interior is preheated
^ the windows are free of ice and condensation
^ the engine is preheated
The use of the stationary heater reduces:
^ the accident hazard by providing clear visibility 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 protect the environment by reducing the pollutants in the exhaust when starting up a preheated 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 below 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 auxiliary heater metering pump (M46/1) 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 (Y16).
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 (N72/1s30) be triggered.
In the instrument cluster up to three preselect times can be stored, of which only one can be activated. The preselection times are shown via the multifunction display (A1p13) in the instrument cluster.
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.
Safety shutoff in the event of crash
The restraint systems control unit (N2/7) sends the crash signal via the Controller Area Network bus class C (engine compartment) (CAN-C) to the central gateway control unit (N93), which issues the signal on the Controller Area Network bus class B (interior) (CAN-B). The front SAM control unit (N10) receives the crash signal and switches the heater unit permanently off. The safety shutoff can only be reset via diagnosis.
Shutoff via thermal fuse
In the event of a temperature control fault or a fault due to overheating, e.g. as a result of a lack of water, the thermal fuse switches the heater unit permanently off when a temperature of 125 °C is exceeded.
Operation after shutoff
^ via the thermal fuse resumes:
^ via diagnosis or by breaking the contact of the power supply for a short period of time
(e.g. removing the fuse). To do this, the STH switch must first be operated for at least 5 s up to a maximum of 15 s. After releasing the STH switch, the fuse must be removed within 30 s to achieve a reset of the thermal fuse.
Engine start during stationary heater operation
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, the engine initially heats itself and only starts to heat the interior once the coolant temperature in the vehicle's engine (large circuit) exceeds the temperature of the heat exchanger (small circuit).
Teach-in of the STH transmitter
Before initial startup, it is necessary to teach in the transmitters allocated to the STH radio remote control receiver (A6/1). For this purpose, the STH switch must be pressed for approx. 20 s until the red indicator lamp in the STH switch flashes on and off.
Release the STH switch as soon as the red indicator lamp is flashing. A time window of 5 s is now open that can be used to teach in. The "OFF" button on the transmitter key must be pressed during this period.
The STH radio remote control receiver remembers the first incoming valid signal and the time window closes.
The procedure must be repeated to teach in another transmitter key. The STH radio remote control receiver stores a maximum of 3 transmitters. If a fourth transmitter is added, the transmitter that was first taught in is deleted.
The time window to teach in the stationary heater transmitter and the number of stationary heater transmitters that have been taught in can be opened or read out via the diagnosis.
Switchover between stationary heater and stationary ventilation
The AAC [KLA] control and operating unit (N22) (with code (580) Automatic air conditioning) or the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning) can correct its heating or ventilation decision as and when needed. During a heating period, switching between ventilation and heating may occur, depending on temperature behavior.
