GF67.29-P-0003RC Heated Rear Window, Function

GF67.29-P-0003RC Heated Rear Window, Function

Function requirements, general
^ No overvoltage or undervoltage
^ Circuit 15 On
^ Vario roof closed and locked

Terminal status c. 15 is provided by the EIS control unit (N73) to the interior CAN.
The convertible top mechanism control unit (N52) transmits the status of the Vario roof to the rear SAM control unit with fuse and relay module (N10/2) via interior CAN.

Heated rear window, general
Actuation of the heated rear window (R1) serves to defrost the rear window and keep it free thereby providing the driver with a clear view to the rear.

The heated rear window function comprises the following partial functions:
^ Manual on/off function sequence
^ Function sequence for operating time
^ Function sequence for consumer shutoff

Manual on/off function sequence
By pressing
- the rear window heater switch (N18s1) on the HEAT control and operating unit (N18) (without code (580) Automatic air conditioning and without code (581) Comfort automatic air conditioning),
- the rear window heater switch (N22s1) on the AAC control and operating unit (N22) (with code (580) Automatic air conditioning),
- the rear window heater switch (N22/7s1) in the AAC comfort control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning)

the heated rear window is switched on.
The corresponding control and operating unit directly reads in the status of the rear window heater switch and transmits the switch on request to the rear SAM control unit via interior CAN. The rear SAM control unit actuates the rear window heater relay (N10/2kE) and thereby switches on the rear window heater.

Actuation of the LED in the rear window heater switch signals that the rear window heater is actuated.

Function sequence for operating time
The operating time of the rear window heater is calculated by the rear SAM control unit depending on the outside temperature and vehicle speed.
For this purpose, the signal from the outside temperature indicator temperature sensor (B14) is provided by the driver-side rear SAM control unit with fuse and relay module (N10/1) and information on the vehicle speed is provided by the instrument cluster (A1) to the interior CAN. The rear SAM control unit Fond reads in all relevant information, evaluates them and actuates the rear window heater via the rear window heater relay.
The operating time of the rear window heater is t = 6 min. under normal conditions.
At outside temperatures of T < 5 °C the operating time is extended by t = 30 s per 1 °C drop in temperature up to a maximum of t = 6 min. (corresponds to T = -7 °C).

At outside temperatures of T < 0 °C the operating time of the rear window heater is extended with increasing vehicle speed

Additional duty cycle depending vehicle speed:
- v > 60 km/h, t = 1 min.
- v > 70 km/h, t = 2 min.
- v > 80 km/h, t = 3 min.
- v > 100 km/h, t = 5 min. (maximum value)

Function sequence for consumer shutoff
If the rear SAM control unit recognizes an undervoltage of U ≤ 10.8 V for min. t = 5 s during the heating phase, it switches the rear window off.

The LED in the rear window heater switch flashes at a frequency of H = 1.5 Hz. If the on-board power supply voltage increases to a normal value of U ≥ 11.6 V with t = 30 s, the rear window heater is switched on automatically and the LED is actuated permanently. However, the voltage is too low for longer than t = 30 s, the heated rear window is switched off completely. It must then be switched back on again manually.

At overvoltages of U ≥ 17 V the rear window heater is also switched off and must be switched on manually thereafter.