GF83.70-P-4200RT STH Control Unit, Component Description
GF83.70-P-4200RT STH Control Unit, Component Description
- Only ECE-cars
Component Identification:
Location
The STH control unit is integrated in the STH heater unit (A6), which is located in the fender in the top right behind the front wheel.
Task
The STH control unit ensures that the vehicle interior is heated or ventilated to the target temperature set at the AAC [KLA] control and operating unit (N22).
The AAC [KLA] control and operating unit decides, depending on the outside or inside temperature, whether heating or ventilation is required
Cooling down to below the outside temperature is not possible during ventilation.
Reading in of sensors integrated in the STH heater unit
^ Glow pin unit flame monitor (A6r4)
^ Temperature sensor (A6b1)
^ Thermal fuse (A6f1)
Control and power supply of internal components
^ Combustion air blower (A6m2)
^ Glow pin unit flame monitor
^ Fuel preheating system (A6r5) (diesel only)
Control and power supply of external components
^ STH switchover valve (Y16)
^ Auxiliary heater metering pump (M46/1)
Control of external components
^ Blower motor (A32m1)
Safety shutoff if an accident occurs
The restraint systems control unit (N2/7) transmits the crash signal via CAN-C to the central gateway control unit (N93), which places the signal on CAN-B. The front SAM control unit (N10) receives the crash signal and switches the stationary heater permanently off. The safety shutoff can only be reset via diagnosis.
Shutoff via thermal fuse
In the event of a temperature control error or due to overheating, e.g. as a result of a lack of water, the thermal fuse switches the STH heater unit permanently off when 125 °C are 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 (N72/1s30) 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.
Discrete inputs:
^ Circuit 30
^ Circuit 31
^ STH radio remote control receiver (A6/1)
Discrete outputs
^ Auxiliary heater metering pump
^ STH switchover valve
Operating time for heater and ventilation
In the basic setting, the maximum heating time is 50 min. It is possible to change it via diagnosis in 10 min increments between 10 and 60 min.
The maximum ventilation time is limited to a maximum of 50 min in the basic setting, as is the heating time, unless a shortening factor was set via diagnosis.
The following shortening factors can be set:
^ Factor 1: ventilation time = 1/3 heating time
^ Factor 2: ventilation time = 1/2 heating time
^ Factor 3: ventilation time = 1/4 heating time