GF83.70-P-0006LE Stationary Heater (STH), Function
GF83.70-P-0006LE Stationary Heater (STH), Function
- with CODE (228) Stationary heater
General function requirements
^ Sufficient remaining quantity of fuel in tank
Stationary heater (STH), general
In cold seasons before commencing a journey, the stationary heater ensures:
- the interior compartment 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
- the amount of accumulated heat is reduced
It is not possible to reduce the temperature below the outside temperature.
Heating or ventilation mode can be triggered in the following ways:
- Immediately using the STH/residual heat button (N72/1s30) (model 216) or the STH/HB [ZUH]/residual heat button (N72/1s30) (model 221) or the STH radio remote control transmitter (A8/3)
- preprogrammed via the instrument cluster (A1)
The central component is the STH heater unit (A6) (model 216) or the STH or HB [ZUH] heater unit (A6) (model 221). The STH heater unit comprises all components necessary for generating and exchanging heat.
The STH heater unit is directly connected to the heating and cooling circuit of the vehicle engine. The fuel for the heater unit is supplied via the STH fuel metering pump (Y23) (model 216) or the STH or HB [ZUH] fuel metering pump (Y23) (model 221).
The STH function comprises the following subfunctions:
^ Function sequence, teach-in of STH transmitter
^ Function sequence, trigger immediate heating mode with STH transmitter
^ Function sequence, trigger immediate heating mode with STH button
^ Function sequence, programming of preselection time
^ Function sequence, trigger heater preselect mode
^ Function sequence, decide to heat or ventilate
^ Function sequence, heating mode
^ Function sequence, ventilation mode
^ Function sequence, component test
^ Function sequence, heat boosting function when driving (with diesel engine)
^ Function sequence, STH shutoff
Function sequence, teach-in of 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. For this purpose, the STH button must be pressed for approx. t = 20 s until the red LED in the STH button flashes on and off.
The actuation of the STH button is read in by the upper control panel control unit (N72/1) and transmitted via interior CAN (CAN B) to the STH control unit (A6n1) (model 216) or the STH or HB [ZUH] control unit (A6n1) (model 221).
After the STH button has been actuated for approx. t = 20 s, the STH control unit transmits feedback in the opposite direction to the upper control panel control unit and the red indicator lamp in the STH button is triggered to flash.
As soon as the red LED starts to flash, the STH button must be released to open the teach-in period window. The request to open the teach-in period window is read in by the upper control panel control unit and transmitted to the STH control unit via interior CAN. This transmits the request to the STH receiver, the teach-in period window is opened for max. t = 5 s.
The OFF button on the STH transmitter must be pressed during this period.
On model 221 the transmitter signal is transmitted by the STH transmitter via radio to the telephone antenna (A2/49a1). The telephone antenna is integrated into the telephone and GPS roof antenna (A2/49). From there, the signal is sent to the STH reception part or to the telephone/cell phone/STH radio remote control antenna splitter (A2/53) (up to 31.5.09 with code (386) Preinstallation for telephone "cell phone" UPCI [UHI] system or as of 1.6.09 with code (386) Comfort telephony) and further to the STH reception part.
On model 216 the transmitter signal is transmitted by the STH transmitter via radio to the stationary heater antenna (Telestart) (A2/27). From there the signal is transmitted directly to the STH receiver.
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 three STH transmitters. If an additional STH transmitter undergoes teach-in, then the STH transmitter that underwent teach-in first is deleted.
Teach-in window can also be opened using the IS tester. The various opening times can only be configured using the IS tester, similarly the number of STH transmitters that have undergone teach-in are read out.
The radio signal path is bidirectional i.e. if a radio signal does not reach the STH receiver, this is displayed on the STH transmitter.
The range of the stationary heater transmitter is s = 300 m. External influences can reduce the range, these include:
- radio interference
- solid obstacles (e.g. enclosed premises)
- unfavorable position to the vehicle
Function sequence, trigger immediate heating mode with STH transmitter
If the "ON" button on the stationary heater transmitter is pressed, the switch-on signal is transmitted by radio.
On model 221 the telephone antenna records the switch-on signal and routes it over the antenna splitter to the STH receiver. On model 216 the switch-on signal is recorded by the stationary heater antenna and forwarded to the STH receiver.
The STH receiver transmits the switch-on signal to the STH control unit, which transmits the "Ventilate" or "Heat" query via interior CAN to the AAC [KLA] control unit (N22/1).
The radio signal path is bidirectional i.e. if a radio signal does not reach the STH receiver, this is displayed on the STH transmitter.
The range of the stationary heater transmitter is s = 300 m. External influences can reduce the range, these include:
- radio interference
- solid obstacles (e.g. enclosed premises)
- unfavorable position to the vehicle
Function sequence, trigger immediate heating mode with STH button
When the STH button is actuated, the switch-on signal is read in by the upper control panel control unit and transmitted via interior CAN to the STH control unit, which transmits the query "Ventilate" or "Heat" to the AAC [KLA] control unit via interior CAN.
Function sequence, programming of preselection time
The function sequence for preselection time programming comprises the following subfunctions:
^ Function sequence, programming of preselection time via the COMAND controller unit (A40/3)
^ Function sequence, programming of preselection time via STH transmitter
The preselection time corresponds to the desired departure time.
Additional function requirements, programming of preselection time via the COMAND controller unit
^ Circuit 15R
Function sequence, programming of preselection time via the COMAND controller unit
The preselection time is configured and activated in the COMAND controller unit with the aid of the front central operating unit (A40/9). The request is transmitted in the process to the COMAND controller unit via the telematics CAN (CAN A).
This is indicated on the COMAND display (A40/8) (without code (867) SPLITVIEW) or SPLITVIEW display (A40/10) (with code (867) SPLITVIEW), which is actuated by the COMAND control unit. The preselection time is saved in the STH control unit.
In the process the preselection time is transmitted from the COMAND controller unit via central CAN (CAN F) to the central gateway control unit (N93). This transmits the preselection time to the STH control unit via interior CAN.
The STH control unit stores a maximum of three preselection times.
After making the selection, the preselection time must also be activated using the front central operating unit. Activation is indicated by the yellow indicator lamp in the STH button. Actuation takes place from the STH control unit to the upper control panel control unit via interior CAN. The yellow indicator lamp goes out after the STH is switched on.
If a preselection time has been activated, the STH control unit transmits this for saving via interior CAN to the central gateway control unit and on from there via central CAN to the instrument cluster.
The instrument cluster stores a preselection time which has been activated.
Function sequence, programming of preselection time via STH transmitter
The preselection time can also be configured and activated using the STH transmitter. The preselection time is set using the arrow buttons and the ON/OFF button and can be activated using the ON button by selecting the corresponding preselection time.
On model 221 the preselection time is transmitted to the telephone antenna and forwarded over the antenna splitter to the STH receiver.
On model 216 the preselection time is transmitted to the stationary heater antenna and forwarded to the STH receiver.
The STH receiver transmits the preselection time for saving to the STH control unit. The STH control unit stores a maximum of three preselection times.
If a preselection time has been activated, the STH control unit transmits this for saving via interior CAN to the central gateway control unit and on from there via central CAN to the instrument cluster.
The instrument cluster stores a preselection time which has been activated.
Activation is indicated by the yellow indicator lamp in the STH button. Actuation takes place from the STH control unit to the upper control panel control unit via interior CAN. The yellow indicator lamp goes out after the STH is switched on.
The radio signal path is bidirectional i.e. if a radio signal does not reach the STH receiver, this is displayed on the STH transmitter.
The range of the stationary heater transmitter is s = 300 m. External influences can reduce the range, these include:
- radio interference
- solid obstacles (e.g. enclosed premises)
- unfavorable position to the vehicle
Additional function requirements for triggering heater preselect mode
^ Circuit 15C OFF
^ Preselection time activated
Function sequence, trigger heater preselect mode
After a preselection time has been activated, the instrument cluster calculates the time remaining until the preselection time based on the current time and activated preselection time.
One hour before the entered preselection time, the instrument cluster transmits a query to the AAC control unit to determine the period of heating/ventilation that is actually required. The request is sent via the central CAN to the central gateway control unit and from there to the AAC control unit via the interior CAN.
Based on the current outside and interior temperature measurements, the AAC [KLA] control unit determines the optimal duration of heating/ventilation.
The outside temperature is measured by the outside temperature indicator temperature sensor (B14) and is read in by the front SAM control unit with fuse and relay module (N10/1). This transmits the temperature value to the AAC [KLA] control unit via interior CAN. The interior temperature is recorded by the in-car temperature sensor (B10/4) and read in directly by the AAC [KLA] control unit. The heating/ventilation time is transferred via the interior CAN to the central gateway control unit and from there on to the instrument cluster via the central CAN. The instrument cluster determines the switch-on time based on the preselection time and the required period of heating/ventilation.
The instrument cluster sends the switch on command to the central gateway control unit via the central CAN to determine the switch on time. This sends the request, via the interior CAN, to the STH control unit, which transmits the "Ventilate" or "Heat" query via interior CAN to the AAC control unit.
The preselection time corresponds to the desired departure time.
The activation via a current preselection time is suppressed if heating mode has been switched on manually in the meantime.
Function sequence, decide to heat or ventilate
The STH control unit transmits the query "Ventilate" or "Heat" via interior CAN to the AAC [KLA] control unit. This determines the current interior and outside temperature as described above under Function sequence, trigger heater preselect mode. It then decides whether to "Ventilate" or "Heat" depending on the values determined and the last setting of the AAC [KLA] control unit.
The red indicator lamp in the STH button lights up while the decision is being made. The indicator lamp is actuated from the STH control unit to the upper control panel control unit via interior CAN. After t = 2 s, the STH control unit is informed of the decision to "Ventilate" or "Heat" via interior CAN and heating or ventilation mode is switched on.
The decision is indicated visually by the indicator lamp in the STH button. The red indicator lamp indicates stationary heating, and the blue lamp indicates stationary ventilation. The indicator lamp is actuated as already described above.
The STH control unit also reports the status back to the STH transmitter.
The following messages may be displayed on the STH transmitter:
- "FAIL": No wireless connection or heater operation not possible (note corresponding symbol)
- "ON": STH activated
- "OFF": STH deactivated
When the STH is switched on, a query on the status of all components involved in the heating mode is conducted and a selftest is performed if 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.
Function sequence, heating mode
After the decision to "Heat" is made, the STH control unit starts the heating mode. The combustion air blower (A6m2) is actuated and runs almost at maximum speed. The glow pin of the flame monitor glow pin unit (A6r4) is switched on. The preglow time of approx. t = 30 s starts. After the preglow time, the combustion air blower is switched off briefly and the fuel metering pump starts to pump fuel. The combustion air blower starts up again and, like the fuel metering pump, increases its speed and output to full load within the next approx. t = 60 s.
The fuel and the combustion air form the fuel/air mixture in the combustor housing. Once the increase in the flow of combustion air and fuel delivery has been completed, the glow pin of the flame monitor glow pin unit is switched off, and the safety period begins for approx. t = 45 s to check the flame.
After the end of the safety period and during heating mode, the flame monitor glow pin unit reports the following states in its function as flame monitor:
- "hot" = sufficient combustion, heater operation continues.
- "cold" = no flame, flame-out or insufficient flame formation, the fuel metering pump is switched off.
With a gasoline engine, startup is repeated once. If there is still no flame formation, fuel supply is stopped by switching off the fuel metering pump and fault shutoff with combustion air blower run-on takes place.
Heater operation is controlled automatically depending on the coolant temperature.
Possible states are:
- Full load operation
- Partial load operation
- Control interval
The STH switchover valve (Y16) is closed at coolant temperatures of T < 60 °C (small coolant circuit). As of T = 60 °C, it is pulse actuated by the STH control unit and the large coolant circuit is then also heated. The coolant circulation pump (M13) ensures that the temperature-controlled coolant is circulated in the coolant circuit. The actuation takes place from the AAC [KLA] control unit via interior CAN to the front SAM control unit and from there directly to the heater circulation pump.
If the temperature is adequate, the AAC control unit actuates the blower regulator (A32n1) via the climate control LIN (LIN B8). This actuates the blower motor (A32m1) directly.
The stationary heater primarily heats up the vehicle interior. Heating of the engine coolant is a secondary function. If the engine is started during heating mode, the engine first heats up itself, then starts to heat the interior once the coolant temperature in the engine (large circuit) has exceeded the temperature of the heat exchanger (small circuit).
Depending on the interior temperature, a switchover from stationary heating to stationary ventilation and vice versa can be made.
When the preselection time is reached, the stationary heater remains on for another t = 5 min and then switches off automatically.
Function sequence, ventilation mode
After the decision is made to "Ventilate", only the blower in the vehicle is actuated. The AAC [KLA] control unit actuates the blower regulator via the climate control LIN, which then actuates the blower motor.
Depending on the interior temperature, a switchover from stationary ventilation to stationary heating and vice versa can be made.
Function sequence, component test
When the STH is switched on, a check is made to determine whether a component fault was stored during the previous heate operation (component status) or whether the STH heater unit is disabled due to fault or overheating.
If a relevant fault is found to be stored in the STH control unit, no start attempt is made and a component test is performed instead. If no more faults are detected during this test, the component status is set to OK for the next switch-on attempt.
The following components are monitored for open circuit, short circuit and proper operation during startup and during heater operation:
- Temperature sensor (A6b1)
- Thermal fuse (A6f1)
- Fuel preheating system (A6r5) (with diesel engine)
- Combustion air blower
- Glow pin unit flame monitor
- Fuel metering pump
- STH switchover valve
If a fault is detected, the heater operation startup process or heater operation is only aborted if the faulty component is essential for operation.
This is not the case for the STH switchover valve. A fault at the STH switchover valve does not result in the termination of heating mode. The STH switchover valve is not taken into account when assessing the component status.
The tank content is also checked during STH startup. The tank status is stored every time circuit 15 is switched off so that the information is available immediately upon startup. Heater operation is only started if there is enough fuel left in the tank.
Compliance with the tank reserve signal can be disabled using the IS tester.
Additional function requirements for heat boosting function when driving
^ Circuit 61
Function sequence for heat boosting function when driving
After an engine start and during the warm-up phase, the heat boosting function ensures that the engine reaches its operating temperature faster and the vehicle interior is heated more quickly. For this purpose, heat boosting takes place automatically with the STH heater unit.
The heat boosting function is activated automatically if:
- Outside temperature is T < 8 °C or
- Coolant temperature is T < 72 °C
The heat boosting function is switched off automatically at a coolant temperature of T > 82 °C
The heat boosting function can also be switched on manually using the STH button at outside temperatures of T > 8 °C to increase comfort.
The red LED in the STH button lights up when heat boosting operation is active.
Function sequence, STH shutoff
The STH shut-off function sequence comprises the following subfunctions:
^ Function sequence, terminate heating mode
^ Function sequence, terminate ventilation mode
^ Function sequence, consumer shutoff by the front SAM control unit
^ Function sequence, shutoff due to overheating
^ Function sequence, consumer shutoff due to overvoltage or undervoltage
^ Function sequence, safety shutoff due to crash
Function sequence, terminate heating mode
Heating mode is terminated automatically by the STH control unit or it can be manually aborted early using the STH transmitter or STH button. With the basic setting, the maximum heating time is t = 50 min. This can be changed with the IS button in 10-minutes intervals within the time range of t = 10 min and t = 60 min.
The combustion is terminated by switching the fuel metering pump off. The run-on time of the combustion air blower starts. The run- on time and speed of the combustion air blower depend on the operating condition (full-load operation, partial load operation or control pause) from which the STH heater unit was switched off.
If the engine is started during heating mode, expiration of the heating time is ignored and the system continues to heat until the coolant temperature of the engine (large circuit) exceeds the temperature of the heat exchanger (small circuit) by T = 5 °C.
Function sequence, terminate ventilation mode
Ventilation mode is terminated automatically by the STH control unit or it can be manually aborted early using the STH transmitter or STH button. With the basic setting, the maximum ventilation time is limited to t = 50 min, as is the heating time. This can be changed with the IS button in 10-minutes intervals within the time range of t = 10 min and t = 60 min.
Several shortening factors can also be set using IS tester.
The following shortening factors are possible:
- Factor 1: ventilation time = 3/4 heating time
- Factor 2: ventilation time = 1/2 heating time
- Factor 3: ventilation time = 1/4 heating time
Additional function requirements, consumer shutoff by the front SAM control unit
^ Circuit 15R
Function sequence, consumer shutoff by the front SAM control unit
To prevent the battery from being discharged, the state of charge in the on-board electrical system is continuously evaluated. The battery sensor (B95) together with the front SAM control unit is responsible for on-board electrical system management.
Voltage, current and temperature at the on-board electrical system battery (G1) are measured by the battery sensor and the condition of the battery is determined from this. Via the on-board electrical system LIN (LIN B7), the battery sensor relays the measured values to the front SAM control unit and calculates the state of charge based on the measured values.
If the voltage drops below a specific voltage value, the front SAM control unit switches off any consumers that require large currents until the state of charge is acceptable again. This also applies for the stationary heater.
Function sequence, shutoff due to overheating
If the temperature of T = 125 �C is exceeded in the STH heater unit, the thermal fuse detects overheating and triggers the heater unit fault run-on process for approx. t = 120 s followed by fault interlock.
Operation after shutoff via the thermal fuse resumes:
- with IS button or
- via temporary interruption of the power supply (e.g. fuse removal). To do this, the STH button must first be operated for at least t = 5 s up to a maximum of t = 15 s. After releasing the STH button, the fuse must be removed within t = 30 s to achieve a reset of the thermal fuse.
Function sequence, consumer shutoff due to overvoltage or undervoltage
As protection against overvoltage and undervoltage and as a redundancy for the shutoff via the front SAM control unit, the STH control unit is equipped with its own voltage monitor and switches off in the event of an overvoltage or an undervoltage.
If the voltage is below the undervoltage limit of U < 11.3 V (for diesel engine) or U < 11 V (for gasoline engine) for longer than t = 2 min (for diesel engine) or t = 4 min (for gasoline engine), the STH heater unit is switched off. Correspondingly, the shutoff takes place if the voltage exceeds the overvoltage limit of U > 15.5 ± 0.3 V for a period of t = 6 + 1 s.
Function sequence, safety shutoff due to crash
When a crash signal is received, the restraint systems control unit (N2/7) transmits a shutoff request to the central gateway control unit via chassis CAN (CAN E). This switches off the STH heater unit permanently by means of the STH control unit via interior CAN. The shutoff process can only be reset using the IS tester.
