Part 2
GF83.70-P-0006FQ Stationary Heater (STH), Function
MODEL 218
- with CODE (228) Stationary heater
During the heating mode, the glow plug/flame monitor unit, in its function as flame monitor, reports:
- "Hot" = sufficient combustion, heater operation continues.
- "Cold" = no flame, flame-out or insufficient flame formation, the fuel pump is switched off and a repeat start-up is initiated once. If there is still no flame formation, the fuel supply is stopped by switching off the fuel pump and a fault shutoff with combustion air blower run-on occurs.
The heater operation is controlled automatically depending on the coolant temperature. Possible statuses:
- Full load operation
- Partial load operation
- Control interval
Following the "Heat" decision, the control and operating unit sends the request to switch on the coolant circulation pump (M13/5) via interior CAN to the front SAM control unit. The front SAM control unit then directly actuates the coolant circulation pump. The temperature- controlled coolant is circulated.
At the same time, the control and operating unit actuates the blower motor via the blower regulator.
The stationary heater primarily heats the vehicle interior via the heat exchanger of the vehicle heating (small circuit).
If the coolant reaches a temperature of T = 40 °C, the blower motor is activated.
As of a coolant temperature of T = 60 °C, the switch hover valve gradually activates the cooling circuit of the engine (large circuit) upon request by the stationary heater control unit.
Depending on the interior temperature, a switchover from stationary heating to stationary ventilation and vice versa can be made.
Upon reaching the departure time the stationary heater is switched on for t = 5 min. and then automatically switches off.
Function sequence for triggering immediate mode
The immediate mode can either be triggered via the stationary heater button or the radio remote control transmitter.
Triggering immediate mode via the radio remote control transmitter can be found in the subfunction "Operation with the radio remote control transmitter".
Pressing the stationary heater button activates the stationary heater.
The upper control panel control unit reads in the status of the stationary heater button directly and sends this via instrument panel LIN, front SAM control unit and interior CAN to the stationary heater control unit.
The stationary heater control unit sends the query "Ventilate or heat" via interior CAN to the control and operating unit. The stationary heater is activated in accordance with the feedback.
The further procedure is the same as for the subfunction "Ventilation or heating mode".
Function sequence for programming the departure time and triggering ventilation/heating mode
The departure time can be programmed and activated via the menu "Settings" in the menu level "Heating" of the instrument cluster or via the radio remote control transmitter.
A maximum of three departure times can be programmed.
Activation of a corresponding departure time is signaled visually by the actuation of the yellow indicator lamp in the stationary heater button.
The stationary heater control unit sends the corresponding request via interior CAN, front SAM control unit and instrument panel LIN to the upper control panel control unit, which then actuates the yellow indicator lamp in the stationary heater button.
The function sequence for programming the departure time and triggering ventilation/heating mode comprises the following subfunctions:
^ Function sequence for programming the departure time via the left multifunction steering wheel button group
^ Function sequence for programming the departure time via radio remote control transmitter
^ Function sequence for triggering ventilation/heating mode for the departure time
Additional function requirements for programming the departure time via the multifunction steering wheel button groups
^ Circuit 15R ON
The electronic ignition lock control unit sends the status of circuit 15R via interior CAN.
Function sequence for programming the departure time via the left multifunction steering wheel button group
The departure time menu is called up in the instrument cluster via the left multifunction steering wheel button group.
The steering wheel electronics (N135) reads in the request directly and sends this via steering LIN (LIN E1), steering column tube module control unit (N80) and chassis CAN to the instrument cluster.
The departure time is displayed in the multifunction display (A1p13) of the instrument cluster. The departure time can then be set and activated in accordance with the menu navigation via the left multifunction steering wheel button group.
If a departure time was activated, the instrument cluster transmits the selected departure time via the interior CAN to the stationary heater control unit. The stationary heater control unit stores the departure time and reports this back to the instrument cluster, which also stores the selected departure time.
Function sequence for programming the departure time via radio remote control transmitter
Alternatively, the departure time can be set and activated using the radio remote control transmitter.
Set the departure time with the left or right arrow buttons and activate it by pressing the "ON" button.
The radio remote control transmitter then transmits a radio signal to the multifunction antenna.
The multifunction antenna forwards the signal via a direct line (without code (386) Comfort telephony) or via the mobile phone and stationary heater radio remote control antenna splitter (with code (386) Comfort telephony) to the radio remote control receiver.
The radio remote control receiver sends the departure time as a switch signal to the stationary heater control unit.
The stationary heater control unit then sends the departure time via interior CAN to the instrument cluster, which stores the selected departure time. The stationary heater control unit then also stores the selected departure time.
Additional function requirements for triggering ventilation/ heating mode for the departure time
^ Circuit 15C OFF, exception: Between the activation of the departure time and the switching on of the stationary heater, circuit 15C was constantly on.
^ Activated departure time
The electronic ignition lock control unit sends the status of circuit 15C via interior CAN.
Function sequence for triggering ventilation/heating mode for the departure time
The instrument cluster queries the required ventilation/heating duration for the desired specified temperature from the control and operating unit approx. t = 60 min. before the desired departure time.
To do so, the instrument cluster sends a corresponding query via interior CAN to the control and operating unit.
The control and operating unit then determines the values of the following variables:
- Ambient temperature
- Interior temperature in the area of the roof
- Interior temperature in the area of the instrument panel
The control and operating unit uses the measured temperature values to determine the difference between the specified and the actual value. Then the control and operating unit calculates the required heating/ventilation duration in order to adjust the actual temperature to the specified temperature. The control and operating unit then sends this value via interior CAN to the instrument cluster.
The instrument cluster uses the heating/ventilation duration and the current time to calculate the switch-on time.
Once the switch-on time is reached, the instrument cluster transmits the request to switch on the stationary heater to the stationary heater control unit. The stationary heater control unit then transmits the query "Heat or ventilate" via interior CAN to the control and operating unit.
The stationary heater is activated in accordance with the feedback from the control and operating unit and the yellow indicator lamp is deactivated.
A switch-on signal sent by the instrument cluster due to an activated departure time is suppressed if the ventilation/heating mode was triggered manually in the meantime.
The further procedure is the same as for the subfunction "Ventilation or heating mode".
Function sequence, STH shutoff
The function sequence for switching off the stationary heater comprises the following subfunctions:
^ Function sequence, terminate heating mode
^ Function sequence, terminate ventilation mode
^ Function sequence, shutoff due to overheating
^ Function sequence for consumer shutoff in the event of undervoltage
^ Function sequence, safety shutoff due to crash
Function sequence, terminate heating mode
Heating mode is terminated automatically by the stationary heater control unit or it can be manually terminated in advance using the radio remote control transmitter or the stationary heater button. With the basic setting, the maximum heating time is t = 50 min. This can be changed in t = 10 min steps between t = 10 min and 60 min using the diagnostic tester. Combustion is terminated by switching off the fuel pump.
If the engine is started during heating mode, expiration of the heating time is ignored and heating continues until the difference between the coolant temperature of the engine (large circuit) and the temperature of the coolant at the coolant outlet of the heater is maximum T = 5 °C.
Function sequence, terminate ventilation mode
Ventilation time is terminated automatically by the stationary heater control unit or it can be manually terminated in advance using the radio remote control transmitter or the stationary heater button. With the basic setting, the maximum ventilation time is t = 50 min. This can be changed in t = 10 min steps between t = 10 min and 60 min using the diagnostic tester.
In addition, a shortening factor can be set using the diagnostic tester.
The following shortening factors can be set:
- Factor 1: ventilation time = 3/4 heating time
- Factor 2: ventilation time = 1/2 heating time
- Factor 3: ventilation time = 1/4 heating time
Function sequence, shutoff due to overheating
If the temperature of T = 125 °C is exceeded in the heater, the thermal fuse recognizes overheating via the temperature sensor and switches the stationary heater off with subsequent overheating locking.
After being switched off start-up takes place:
- via the diagnostic tester or
- via temporary interruption of the power supply (removal of fuse 75 (N10/2f75)).
For safety reasons proceed as follows here:
1. Press stationary heater button for at least t = 5 up to 15 s.
2. Remove fuse within t = 30 s.
3. Reinsert fuse.
Function sequence for consumer shutoff in the event of undervoltage
To prevent battery discharging, the state of charge in the on-board electrical system is constantly evaluated by the stationary heater control unit.
The following undervoltage limits are valid for operation of the stationary heater:
- Gasoline engine: U = 11.3 V
- Diesel engine: U = 11.5 V
If the listed voltage values are undershot for t > 20 s, the stationary heater control unit switches off the stationary heater.
Function sequence, safety shutoff due to crash
In the event of an accident, the supplemental restraint system control unit (N2/10) sends the request for shutting off via chassis CAN, front SAM control unit and interior CAN to the stationary heater control unit. The stationary heater control unit then permanently switched off the stationary heater. The stationary heater can then only be recommissioned using the diagnostic tester.
