Heated rear window, function - GF67.29-P-0003SK: Notes

MODEL 171.4 

System overview 

Function prerequisites: 

• Circuit 15 ON
• No undervoltage or overvoltage
• Vario roof closed and locked

Function 

When the heated rear window switch (N18s1, N22s1 or N22/7s1) is pressed, the heated rear window (R1) is switched on by the rear SAM control module with fuse and relay module (N10/2).

This is indicated by a function LED in the heated rear window switch (N18s1, N22s1 or N22/7s1).

Pressing again switches the heated rear window (R1) off.

Simultaneously, the function LED in the heated rear window switch (N18s1, N22s1 or N22/7s1) goes out.

The switch-on duration for the heated rear window (R1) depends on the outdoor temperature and the vehicle speed.

The outside temperature indicator temperature sensor (B14) is read in by the driver SAM control module with fuse and relay module (N10/1).The information is relayed to the rear SAM control module with fuse and relay module (N10/2) via the controller area network bus class B (interior compartment) (CAN-B).

The vehicle speed is read in via the instrument cluster (A1) and transmitted to the rear SAM control module with fuse and relay module (N10/2) via the controller area network bus class B (interior compartment) (CAN-B).

Duty cycle 

The minimum switch-on duration of the heated rear window (R1) is 6 min. The maximum switch-on duration is determined by the outdoor temperature and the vehicle speed and is max. 17 min.

If the outdoor temperature is less than 5°C, the minimum switch-on duration is corrected upward by 30 s for each degree of lower outdoor temperature (however, max. 6 min.).

If the outdoor temperature is less than 0°C and the vehicle speed is higher than 60 km/h, the minimum switch-on duration is corrected upward by 1 minute for each 10 km/h increased vehicle speed (however, max. 5 min.)

When the Vario roof is open, the heated rear window (R1) is not switched on. The overhead control panel control module (N70) receives the information from the Vario roof closed (left pin) (S69) and transmits it to the rear SAM control module with fuse and relay module (N10/2) via the controller area network bus class B (interior compartment) (CAN-B).

Switch-on characteristics when voltage is too low 

If the rear SAM control unit with fuse and relay module (N10/2) recognizes an electrical system voltage of less than 10.8 V for min. 5 seconds during the switch-on duration, the rear SAM control unit with fuse and relay module (N10/2) switches off the heated rear window element (R1).

In this case, the function LED flashes in the heated rear window switch with only half of the brightness and 1.5 Hz (N18s1, N22s1 or N22/7s1).

If the electrical system voltage increases again to over 11.6 V within 30 s, the heated rear window (R1) is automatically switched on and the function LED comes on permanently

The ON time continues to elapse during the low voltage period. However, if the low voltage exists for longer than 30 s, the heated rear window (R1) is switched off completely. It must then be switched back on again manually.

Even if the voltage is extremely low or high (electrical system voltage 8 V or greater than 17 V) the heated rear window (R1) is also switched off completely and must then be switched on manually.

The electrical system voltage is read in via the EIS control module (N73) and is transmitted to the rear SAM control module with fuse and relay module (N10/2) via the controller area network bus class B (interior compartment) (CAN-B)

Driver-side SAM control unit with fuse and relay module, location/task/design		GF54.21-P-4109SK
Rear SAM control unit with fuse and relay module, location/task		GF54.21-P-4130SK
Electronic ignition switch control module, location/task		GF80.57-P-4120SK
Overhead control panel control module, location/task/design		GF82.20-P-4110SK
Heating pushbutton control module, location/task	On vehicles without code (580a) Automatic air conditioning, without code (581b) Comfort automatic air conditioning	GF83.20-P-2120SK
Automatic air conditioning control and operating module, location/task	On vehicles with code (580a) Automatic air conditioning	GF83.40-P-2180SK
Comfort automatic air conditioning control and operating module, location/task	On vehicles with code (581b) Comfort automatic air conditioning	GF83.40-P-2181SK
Outdoor temperature sensor, location/task/function		GF83.57-P-2110SK