Rear window heating (Audi 100 C4)

The rear window heating is switched on and off directly by a switch located on the instrument panel. Power is supplied to the switch when the ignition is on from the X-contact unloading relay via the fuse along the white-yellow wire. From there, when the switch is in the appropriate position, power is supplied to the rear window via numerous plug connections in the white wire.

Troubleshooting

If the heated rear window remains cold, the following problems may be the cause:

Faulty fuse.

The switch is faulty. It should be removed (in the manner described in this chapter) and check with a test lamp whether current flows through the white wire when the ignition is on and the switch is pressed.

Remove both pillar trims near the rear window.

Check the wiring to the rear window: Use a test light to check if power is reaching back through the white connecting wire to the window on the left. (The same procedure should be followed on models equipped with a rear window antenna.)

Check on the right pillar whether the ground contact of the glass heating thread is OK.

If the heating filaments are damaged and the electrical circuit is broken, then you can use silver conductive varnish. It is produced, for example, by Doduco, and you can buy it at an auto parts store.