gf6729p9900a

Rear window heating, basic function

Type gf · topic 67.29 · version 0104 · 2020-07-31

Applies to: Model all (CAR)

Where it sits

Function group 3 Body › 67 Windows › 67.29 Heated rear window - electrical system — Series 900 (models 9**) · Series 902 (models 9**) · Series 904 (models 918, 919, 924, 925, 938, 943, 957) · Series 906 (models 917, 918, 924, 953)

EinPAS 36 Visibility › 36.15 Glass pane/window › 36.15.1 Basic information — Series 900 (models 9**) · Series 902 (models 9**) · Series 904 (models 918, 919, 924, 925, 938, 943, 957) · Series 906 (models 917, 918, 924, 953)

Also applies to engines/gearboxes: 139 ***, 254 ***, 256 ***, 272 ***, 276 ***, 282 ***, 457 9**, 541 9**, 542 9**, 608 ***, 700 4**, 700 420, 700 421, 700 422, 700 423, 715 3**, 715 5**, 722 6**, 722 9**, 724 ***, 724 0**, 724 033, 724 044, 724 045, 724 1**, 724 103, 724 114, 724 115, 724 120, 725 ***, 725 0**, 725 035, 725 037, 725 038, 725 085, 725 1**, 739 390, 739 391, 739 395, 739 396, 739 397, 739 398, 739 399, 740 698, 743 3**, 743 4**, 743 498, 746 971, 924 9**, 924 910, 925 9**, 926 9**

GF67.29-P-9900A

Rear window heating, basic function

01.07.2020

Model

all (CAR)

Overview

This document contains the following information:

General

Function requirement

Heat rear window

Shutoff conditions

General

The rear window heater heats the rear window. This allows ice or snow on the rear window to be defrosted and counteracts fogging of the rear window. Depending on the vehicle, the rear window heater is controlled by the central signal acquisition and actuation module or the rear signal acquisition and actuation module.

When the rear window heater is switched on, the outside mirror heating is also activated.

Function requirement

Circuit 15 ON (except pre-entry climate control for hybrid, electric vehicles)

Heat rear window

The rear window heater can be operated manually via the rear window heater switch on the air conditioning control panel and via the voice control system (VCS). The function of the rear window heater is indicated visually.

The rear window heater is automatically activated/deactivated during the pre-entry climate control (hybrid, electric vehicles) or in order to reach the operating temperature of the combustion engine more quickly. The automatically activated rear window heater is not indicated visually.

In vehicles with combustion engines, the actuation of the rear window heater is interrupted or not permitted while the engine is being started.

The duty cycle of the rear window heater is stored in the system. Depending on the outside, interior, and coolant temperature and the vehicle speed, this varies between 2 and 26 min.

Variable

Duty cycle

Additional information

-

15 min

Normal duty cycle

Outside temperature above 50 °C

2 min

To protect the rear window

After start:
Coolant temperature < operating temperature

Maximum 15 min

Only with combustion engines, to increase the engine load

Outside temperature between 5 and -7 °C

+30 s added to the normal duty cycle for each 1 °C below 5 °C

Down to -7 °C corresponds to a maximum of +6 min

Outside temperature below 0 °C at 60 km/h

+1 min added to the determined duty cycle

-

Outside temperature below 0 °C at 70 km/h

+2 min added to the determined duty cycle

-

Outside temperature below 0 °C at 80 km/h

+3 min added to the determined duty cycle

-

Outside temperature below 0 °C at 90 km/h

+4 min added to the determined duty cycle

-

Outside temperature below 0 °C at 100 km/h

+5 min added to the determined duty cycle

At -7 °C, this results in the max. duty cycle of 26 min.

Shutoff conditions

The rear window heater is deactivated by the energy management via the consumer reduction in the case of undervoltage of the on-board electrical system.

In vehicles with a combustion engine, the rear window heater is switched off when the combustion engine is switched off.

Special case: Traffic light stop

If circuit 15 R remains switched on after the combustion engine has been shutoff, the actuation of the rear window heater is interrupted for a certain time. This time is stored in the system and can be adjusted via the vehicle diagnosis system. If the ignition is switched on within the stored time, the rear window heater is activated for the duty cycle that remained before the interruption. After the stored time has passed, the rear window heater must be switched on again as necessary.

Function schematics

Function schematic, heat rear window

Model 118, 177, 247

PE67.29-P-2500-97A

Model 167, 293Model 213, 238, 257, 290 as of model year 2021

PE67.29-P-2500-97B

Additional basic functions

Reduce consumers, basic function

GF54.10-P-1011A

Heating of mirror glass of outside mirror, basic function

GF88.79-P-1001A

Control units

Basic function of signal acquisition and actuation module

Model 118, 177, 247

GF54.21-P-9895A

Basic function of signal acquisition and actuation module at rear

Model 167, 293
Model 213, 238, 257, 290
as of model year 2021

GF54.21-P-9897A

Components

Rear window heater, basic function

GF67.29-P-2006A

Referenced documents