Heat Left/Right Outside Rearview Mirrors Function - GF88.79-P-2000GW
Model 463 (except 463.342)
as of model year 2013
Function requirements, general
- No overvoltage or undervoltage
- On-board electrical system consumer shutoff not active
- Particular (local) front power window not active
Heat left/right outside mirror, general
The mirror heater (M21/1r1) in the left outside mirror (M21/1) and the mirror heater (M21/2r1) in the right outside mirror (M21/2) can be activated in combination with the heated rear window function (model 463.23/24/27/34) or depending on the temperature.
If several requests are present simultaneously, the mirror heaters are always operated at the highest possible actuation power resulting from the corresponding actuation source.
The left front door control unit (N69/1) directly actuates the mirror heater in the left outside mirror. The right front door control unit (N69/2) directly actuates the mirror heater in the right outside mirror.
The heating left/right outside mirror function comprises the following partial functions:
- Temperature-dependent control
- Control in case of active heated rear window function (model 463.23/24/26/27/34)
Additional function requirements for temperature-dependent control
- "Engine running" or "Drive train operational" signal on.
Model 463 (except 463.342)
as of model year 2019
The CDI control unit (N3/9) or the ME-SFI [ME] control unit (N3/10) transmits the "Engine running" signal or "Drivetrain operational" signal via the drive CAN (CAN C1), powertrain control unit (N127) and suspension FlexRay (Flex E) to the electronic ignition lock control unit (N73).
The electronic ignition lock control unit transmits the signal "Engine running" or "Drivetrain operational" signal over the interior CAN (CAN B) to the front door control units.
Model 463 (except 463.342)
as of model year 2013 up to model year 2019
The CDI control unit or the ME-SFI [ME] control unit or the powertrain control unit transmits the "Engine running" signal or "Drivetrain operational" signal via the suspension CAN 1 (CAN E1) to the electronic ignition lock control unit.
The electronic ignition lock control unit transmits the "Engine running" signal or "Drivetrain operational" signal via the interior CAN to the front door control units.
Temperature-dependent control
The mirror heaters are operated depending on the following values:
- Outside temperature
- Dewpoint temperature
The front door control units compare both values with each other and switch the mirror heaters on if a dew point temperature of 2 °C is below the outside temperature.
Outside temperature:
The outside temperature sensor (B14) measures the outside temperature.
In vehicles as of 03.04.2018, the front SAM control unit (N10/6) directly reads in the outside temperature sensor signal, calculates the outside temperature and transmit this via the interior CAN, electronic ignition lock control unit and user interface CAN (CAN HMI) to the instrument cluster (A1).
In vehicles up to 02.04.2018, the SAM control unit (N10) directly reads in the outside temperature sensor signal, calculates the outside temperature and transmits this via the interior CAN to the instrument cluster.
The instrument cluster calculates, taking into account the vehicle speed and engine heat, the outside temperature to be displayed and transmits the calculated, corrected outside temperature value as of 03.04.2018 via the user interface CAN, electronic ignition lock control unit, interior CAN to the front door control units and up to 02.04.2018 via the interior CAN to the front door control units.
If the value of the outside temperature is implausible or not available, the mirror heaters are switched off permanently.
Dew point temperature:
The dew point temperature is the temperature at which water vapor would condense in the outside air. The glass in the mirrors would fog up.
In vehicles as of 03.04.2018, the dew point temperature is detected by the humidity and temperature sensor (B38/2b3) in the rain and light sensor with additional functions (B38/2). The front SAM control unit reads in the signals of the humidity and temperature sensor via the rain and light sensor LIN (LIN B16) and transmits these via the interior CAN to the climate control unit (N22/1). The climate control unit transmits dew point temperature to the front door control unit via the interior CAN.
In vehicles up to 02.04.2018, the dew point temperature is detected by the vehicle interior humidity and temperature sensor (B82). The SAM control unit reads in the signals of the vehicle interior humidity/temperature sensor via the roof LIN (LIN B13) and transmits it to the climate control and operating unit (N22/7) via the interior CAN. The climate control and operating unit transmits the dew point temperature to the front door control units via the interior CAN.
If the vehicle interior humidity and dew point temperature sensor supplies implausible values or no values, a substitute value of 13 °C (programmable via diagnostic tester) is used.
The front door control units actuate the mirror heater in the respective outside mirror in a pulse width modulated (PWM) manner, i.e. in an output-controlled manner.
In the following tables, the actuation duration of the mirror heaters as of 03.04.2018 is listed for different temperature ranges for falling and rising temperatures.
As of 03.04.2018
| Restart or temperature range change at decreasing temperature | Thawing phase | Holding phase | ||
|---|---|---|---|---|
| Temperature range | Duration | PWM value | Duration | PWM value |
| > 5 °C | 2 min | 100 % | Temperature-dependent | 30 % |
| 5 to -5 °C | 5 min | 100 % | Temperature-dependent | 70 % |
| < -5 °C | 10 min | 100 % | Temperature-dependent | 100 % |
As of 03.04.2018
| Temperature range change at increasing temperature | Thawing phase | Holding phase | ||
|---|---|---|---|---|
| Temperature range | Duration | PWM value | Duration | PWM value |
| < -2 °C | 10 min | 100 % | Temperature-dependent | 100 % |
| -2 to 8 °C | 5 min | 100 % | Temperature-dependent | 70 % |
| > 8 °C | 2 min | 100 % | Temperature-dependent | 30 % |
Up to 02.04.2018, the mirror heater is activated for:
- Outside temperature ≤ dew point + 2 °C (can be programmed via diagnostic tester)
- Outside temperature < 15 °C
- Implausible outside temperature value
- Outside temperature value not available
The mirror heater is switched off at:
- Outside temperature dew point + 5 °C (can be programmed via diagnostic tester)
- Outside temperature > 18 °C
Actuation of the mirror heaters is limited to 10 min after starting the engine. After expiration of this time the mirror heaters are switched off.
Additional control function requirement for active heated rear window function (model 463.23/24/26/27/34)
- Circuit 15R ON
The electronic ignition lock control unit transmits the circuit status of circuit 15 over interior CAN to the front door control units.
Control in case of active heated rear window function (model 463.23/24/26/27/34)
In the case of an active heated rear window function, the rear SAM control unit (N10/8) (as of 03.04.2018) or the climate control and operating unit (up to 02.04.2018) transmits the status "Rear window heater active" via the interior CAN to the front door control units.
The front door control units actuate the mirror heater in the corresponding outside mirror.
The mirror heaters are actuated as long as the request is present at a capacity of 100 %. When the heated rear window function is switched off, the mirror heaters are also switched off.
The rear window heater status can be shown in the audio/COMAND display (A40/8).
| Electrical function diagram for mirror heater | Model 463 (except 463.342) as of model year 2019 | PE88.79-P-2055-97ZGB | |
| Model 463 (except 463.342) as of model year 2013 up to model year 2019 | PE88.79-P-2055-97ZGA | ||
| Overview of system components for electric mirror | GF88.79-P-9996GW |