Control Module Malfunction Switch-Off, Function

Voltage too low switch-off
When the front HS and seat ventilation control module (N25/7) recognizes that the voltage is too low, it switches off the heater output stages and the control outputs to the blower regulators for the seat ventilation.

The low voltage switch-off threshold depends on the time expired since circuit 15R ON.

Time expired since C. 15R ON Low voltage switch-off threshold
0 - 4 (±) min 9.6 - 10 V
> 4 min 10.6 - 11 V

When the low voltage switch-off is active, the LEDs next to the control switch flash (f =1.5 Hz ± 20 %); only the LEDs active at the time of switch-off flash.

The switching threshold for switching back on the control module outputs is 0.8 (±0.2) V above the corresponding switch-off threshold.

Voltage too high switch-off
When the control module recognizes that the vehicle electrical system voltage has exceeded 16 ±0.2 V, it switches off the heater output stages and the control output to the blower regulator for the seat ventilation.
The function illumination next to the control switch does not flash following excessive voltage switch-off.

Temperature too high switch-off
The control module has an excessive temperature recognition feature for switching off the affected heater output stage when the temperature is impermissibly high.
The excessive temperature recognition feature is laid out so that heating stage I can be operated continuously and heating stage II twice in sequence (2 x 5 min) without switching off. When the temperature too high switch-off is activated, the function illumination next to the control switch does not flash.

Switch-off in the event of short circuit, short circuit to ground.
When the control module recognizes a short circuit to ground or short circuit (to C. 30 or C. 31), it switches off the affected output. The function illumination does not flash following switch-off due to a short circuit or short circuit to ground.