Heat Left/Right Side View Mirrors Function - GF88.79-P-2000RF
Model 205, 253
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 side view mirror, general
The mirror heater (M21/1r1) in the left side view mirror (M21/1) and the mirror heater (M21/2r1) in the right side view mirror (M21/2) can be activated as follows:
- Priority 1: via heated rear window function
- Priority 2: Via the pre-entry climate control function (with code 577 (Remote activation of heater and ventilation systems) or hybrid vehicle or Model 253.99)
- Priority 3: via temperature-dependent control
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 side view mirror. The right front door control unit (N69/2) directly actuates the mirror heater in the right side view mirror.
The heating left/right side view mirror function comprises the following partial functions:
- Function sequence for mirror heater when rear window is switched on
- Function sequence for mirror heater when pre-entry climate control function is switched on (with code 577 (Remote activation of heater and ventilation systems) or hybrid vehicle or Model 253.99)
- Function sequence for temperature-dependent mirror heater
Additional function requirement for mirror heater when rear window heater function is switched on
- Terminal 15 ON
The electronic ignition lock control unit (N73) sends the status of circuit 15 via interior CAN (CAN B) to the front door control units.
Function sequence for mirror heater when rear window is switched on
With the heated rear window function active, the rear SAM control unit (N10/8) transmits the status "Heated rear window active" via interior CAN to the front door control units. Then the left front door control unit switches on the mirror heater in the left side view mirror. Then the right front door control unit switches on the mirror heater in the right side view mirror. The mirror heaters are actuated at 100% output as long as the request is present. When the heated rear window function is switched off, the mirror heaters are also switched off.
Function sequence for mirror heater when pre-entry climate control function is switched on (with code 577 (Remote activation of heater and ventilation systems) or hybrid vehicle or Model 253.99)
When the pre-entry climate control function is active, the climate control control unit (N22/1) sends the request "Mirror heater On" via interior CAN to the front door control units. Then the left front door control unit switches on the mirror heater in the left side view mirror.
Then the right front door control unit switches on the mirror heater in the right side view mirror. The mirror heaters are actuated at 100% output as long as the request is present. When the pre-entry climate control function is switched off, the mirror heaters are also switched off.
Additional function requirements for temperature-dependent mirror heater
- "Engine running" or "Drive train operational" signal on.
Model 205, 253 (except 253.99)
The "Engine running" or "Drivetrain operational" signal is sent by the CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) over the drive train CAN (CAN C1), powertrain control unit (N127), chassis FlexRay, electronic ignition lock control unit and the interior CAN to the front door control units.
Model 253.99
The powertrain control unit transmits the "Drivetrain operational" signal via the suspension FlexRay, electronic ignition lock control unit and interior CAN to the front door control units.
Function sequence for temperature-dependent mirror heater 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 activate the mirror heaters if the dew point temperature lies at least T = 2 °C under the outside temperature.
Outside temperature:
The outside temperature is detected by the outside temperature sensor (B14). The front SAM control unit (N10/6) directly reads the signal from the outside temperature sensor, uses it to calculate the outside temperature and sends a corresponding signal to the instrument cluster via interior CAN (CAN B), electronic ignition lock control unit (A1) and user interface CAN (CAN HMI). The instrument cluster calculates the outside temperature to be displayed, taking the vehicle speed and the engine heat into consideration, and transmits the corrected outside temperature via the user interior CAN, electronic ignition lock control unit and interior CAN to the front door control units.
If the value of the out side 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.
The dew point temperature is sensed by the humidity and temperature sensor (B38/2b3) in the rain/light sensor with additional functions (B38/2). The rain/light sensor with additional functions sends the dew point temperature via rain/light sensor LIN (LIN B16), front SAM control unit and interior CAN to the climate control control unit. The climate control unit transmits dew point temperature to the front door control unit via the interior CAN.
The left front door control unit actuates the mirror heater in the left side view mirror, the right front door control unit actuates the mirror heater in the right side view mirror.
If the dew point value is implausible or not available, a substitute value of T = 13 °C is used (can be programmed via the diagnostic tester).
The mirror heaters are pulse width modulated (PWM), i.e. actuated with a regulated output.
The following tables show the actuation time of the mirror heaters for various temperature ranges at decreasing or increasing temperature.
| 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 % |
| 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 % |
The mirror heaters are switched off at:
- Outside temperature ≥ dew point temperature 5 °C (can be programmed via diagnostic tester)
- Outside temperature > 18 °C
| Electrical function diagram for mirror heater | PE88.79-P-2055-97FBA | ||
| Overview of system components for electric mirror | GF88.79-P-9996RF |