Heated Windshield, Function - GF67.10-P-0002FG
Model 213
up to model year 2021
with code 597 (Heated windscreen)
Function requirements, general
- No undervoltage or overvoltage
- Terminal 15 ON
The electronic ignition lock control unit sends the status of circuit 15 via interior CAN to the climate control unit.
Heated windshield
The windshield can be heated for deicing purposes and to prevent fogging at outside temperatures below 10°C. The climate control unit regulates and monitors the heated windshield function. One of two operating modes can be specified via the variant coding in the climate control unit.
In the defrost operating mode, the function is operated at 100 % output.
In the AUTOMATIC operating mode, the function is operated in an output-regulated manner depending on the following influencing variables:
- Vehicle non-operational time
- Outside temperature
- Temperature on inside of windshield
- Fogging tendency on inside of windshield
The heated windshield function is activated where the defrost function is triggered or where there is a risk of fogging on the inside of the windshield. The climate control unit calculates - depending on coded operating mode, the specified heating output value and transmits this via the air-conditioning control LIN 2 to the windshield heater control unit. The windshield heater control unit then accordingly actuates the heated windshield. The heated windshield is operated with a voltage of 42 V that is converted by the windshield heater control unit. The windshield heater control unit monitors the function of the heated windshield and sends the corresponding basic data, e. g. power input, temperature or short circuit of heated windshield via the air-conditioning control LIN 2 to the climate control unit.
The climate control unit evaluates the following influencing variables for the control of the function:
- Status of defrost function
The defrost function is started by actuating the defrost button on the climate control operating unit. The climate control operating unit directly reads in the status of the defrost button and transmits this via the air-conditioning operating LIN to the climate control unit. If the defrost button is actuated and the outside temperature is below 10°C, the climate control unit starts the heated windshield function. If the defrost button is actuated again, the climate control unit ends the function.
- Outside temperature
The outside temperature is recorded by the outside temperature sensor. The front SAM control unit directly reads in the outside temperature sensor signals, calculates the outside temperature and sends the data to the climate control unit via interior CAN. At outside temperatures below 10°C, the climate control unit starts the heated windshield function.
- Fogging tendency (fogging index)
The fogging index describes the tendency of the windshield to fog on the inside. The fogging index is referenced via the dew point temperature.
A humidity and temperature sensor is integrated in the rain/light sensor with additional functions. This sensor measures the relative air humidity and temperature directly at the inside of the windshield. These values are used by the rain/light sensor with additional functions to calculate the dew point temperature. An imminent windshield fogging can be detected by comparing the windshield surface temperature with the dew point temperature. The rain and light sensor with additional functions transmits the temperature at the inside of the windshield and the dew point temperature via the rain and light sensor LIN, front SAM control unit and interior CAN to the climate control unit. In the case of imminent fogging, the climate control unit starts the heated windshield function.
- Status of engine running or drivetrain operational
The operation of the heated windshield is comparably energy intensive. So that the on-board electrical system stability is not at risk from the operation of the heated windshield, the climate control unit evaluates the stability of the engine running or in case of engine OFF the "Drivetrain operational" signal. The CDI control unit or ME-SFI [ME] control unit transmits the "Engine running" signal or "Drivetrain operational" signal via the drive CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit and interior CAN to the climate control unit.
- Coolant temperature, non-operational time of vehicle (differentiation between short or long stop)
The coolant temperature is calculated by the CDI control unit or by the ME-SFI [Me] control unit. The CDI control unit or the ME-SFI [ME] control unit sends the coolant temperature via the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and interior CAN to the climate control unit.
The evaluation of the coolant temperature allows for conclusions on the vehicle non-operational time.
- Vehicle speed
The vehicle speed is calculated by the instrument cluster. Information about the vehicle speed is transmitted by the instrument cluster via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control unit.
Defrost mode (100 % output)
If the function is activated by the starting of the defrost function and the temperature at the windshield lies below a specific value, the heated windshield is initially operated for 30 s at 100 %. The climate control unit subsequently regulates the function depending on the temperature of the windshield, coolant temperature and vehicle speed. The climate control unit switches off the function at the latest after 8 min.
The temperature at the inside of the windshield is detected by the humidity and temperature sensor in the rain and light sensor with additional functions. The rain and light sensor with additional functions reads in the signals of the humidity and temperature sensor, calculates the temperature at the inside of the windshield and transmits this via the rain and light sensor LIN, front SAM control unit and interior CAN to the climate control unit.
At the point in time of the function initiation, the climate control unit also evaluates the outside temperature. Where this lies below 10°C, the climate control unit starts the heated windshield function.
Output controlled operation
Where the function is automatically activated via the fogging index, the heated windshield is actuated in an output controlled manner. This means, depending on the probability or existence of windshield fogging, the heated windshield is operated at different heating outputs. The heated windshield is initially operated for 30 s at 100 % output. The climate control unit then regulates the output of the heated windshield depending on the fogging index and vehicle speed between 35 and 100 %. At vehicle speeds above 120 km/h, the climate control unit deactivates the function.
Model 213 with code 357 (Map navigation) or code 531 (COMAND APS):
The windshield can fog up when driving through tunnels and with rising outside temperatures. For this reason, the climate control unit actuates the heated windshield at 100 % output. Once the windshield temperature is 2°C higher than the outside temperature, the climate control unit deactivates the function. Driving through tunnels is detected via the GPS information. The head unit sends the relevant information via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control unit. If the heated windshield is operated at more than 600 W, the climate control unit transmits the "Increase idle speed" request via the interior CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and drive CAN to the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit then increases the idle speed.
The heated windshield is automatically deactivated at outside temperatures above 3°C.
| Electrical function schematic for heated windshield | PE67.10-P-2051-97DBA | ||
| Overview of system components for climate control | GF83.40-P-9994FG |