Comfort Heaters Automatic Shutoff, Basic Function - GF83.20-P-1000A

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Model All (CAR)

with code 443 (Heated steering wheel)

Model All (CAR)

with code 906 (Front armrest heater)

Model All (CAR)

with code 907 (Rear armrest heater)

Overview:

This document contains information on:

General
Function
- Shut-off in the event of a hardware defect
- Shutoff in the event of an error (short circuit, overload or open circuit (line break))
- Switching off by means of energy management
- Shutoff after circuit 15 R off
- Shutoff when the engine starts
- Shutoff due to "timeout error" (only armrest heating)
- Shutoff at end of diagnosis
- Shutoff due to overtemperature of heating elements (only armrest heating)
- Shutoff due to overtemperature of printed circuit boards in control unit (only armrest heating)
- Shutoff due to overtemperature (only steering wheel heater)
- Shutoff after timer control (only steering wheel heater)
- Shutoff in range maximization (depending on model)

General

The comfort heaters switch off automatically under certain conditions. This serves primarily to protect the components and the on-board electrical system.

Function

The comfort heaters switch off automatically under certain conditions. This serves primarily to protect the components and the on-board electrical system.

Shut-off in the event of a hardware defect

If a control unit reports active actuation of a heating element even though no request has been made via the corresponding switch, the corresponding comfort heater is switched off. For the steering wheel heater, the steering wheel electronics store a fault message in the fault memory.

Shutoff in the event of an error (short circuit, overload or open circuit (line break))

The corresponding control unit recognizes a short circuit, overload or line break of the corresponding heating elements and then switches off the power supply.

Switching off by means of energy management

In order to prevent the battery from discharging, the energy management function continuously evaluates the state of charge. Depending on the situation, the energy management function also switches off the comfort heaters. If the comfort heating is switched off, the LEDs in the respective switch initially remain activated. If the on-board electrical system returns to the specified voltage again within a period of approx. 3 min., the comfort heating function is also restarted automatically. If the shutoff lasts longer than approx. 3 min, the LEDs also switch off. If the shutoff continues and is a new switch-on request for the function is made, the LEDs light up for approx. 1.5 s and then go out.

Shutoff after circuit 15 R off

For circuit 15 R off and circuit 15 C on, the timer control runs on for approx. another 5 minutes. If circuit 15 R switches on again, the comfort heating also switches back on again.

Shutoff when the engine starts

During a cold start of the engine, the comfort heaters switch off for approx. 20 s. During a warm start of the engine, the comfort heaters switch off briefly. The timer control continues running and the indicator lamp of the respective comfort heater also remains on.

Shutoff due to "timeout error" (only armrest heating)

The comfort heaters switch off if the actuation request from the signal acquisition and actuation module is canceled or if the electronic ignition lock control unit detects a "timeout period".

Shutoff at end of diagnosis

After diagnosis has finished, the comfort heaters switch off.

Shutoff due to overtemperature of heating elements (only armrest heating)

The respective control unit continuously monitors the temperature of the heating element. If there is a risk of overheating, the corresponding heating element is switched off.

Shutoff due to overtemperature of printed circuit boards in control unit (only armrest heating)

Individual stages are shut off if a preset printed circuit board temperature is reached. When a printed circuit board temperature of more than approx. 90°C is reached, activation of the armrest heating is no longer possible.

Shutoff due to overtemperature (only steering wheel heater)

If the vehicle interior temperature exceeds a value of approx. 30°C, the steering wheel heater switches off. The steering wheel heater indicator lamp remains on. If the vehicle interior temperature drops below a value of approx. 30°C, the steering wheel heater is switched on again automatically. The cutout temperature of the steering wheel heater can be parameterized through the diagnosis tester.

Shutoff after timer control (only steering wheel heater)

After 15 min have elapsed, the steering wheel electronics switch off the steering wheel heater automatically. The steering wheel heater timer control can be parameterized through the diagnosis tester.

Shutoff in range maximization (depending on model)

When range maximization is activated, the comfort heaters switch off. The comfort heaters can be activated again if necessary. This also cancels all other climate control restrictions triggered by the range maximization, and the maximum increase in range is reduced accordingly.