Rear window heater

The defrosting of the rear window is carried out by a heater, which is a series of parallel conductors sprayed onto the glass. When an electric current is passed, the conductors heat up and defrost and clean the rear window from moisture. The current is supplied from a relay located in the body electrical unit.

Examination

• Start the engine and let it run at 2000 rpm^-1.
• Turn on the rear window defroster. Connect the negative lead of the voltmeter to «weight» car. Connect a voltmeter lead in turn to the center of each conductive strip of the rear defroster (pic. 19.107). The voltmeter should show a voltage of about 6 V.

• If at point A the voltmeter shows a voltage of 12 V, then the conductive strip of the heater has a break on the side between the voltmeter connection point and the side of the heater connected to «weight».
• If the voltmeter shows a voltage below 0 V; this means that the conductive strip of the heater has a break on the side between the connection point of the voltmeter and the side of the heater connected to the positive terminal of the battery.
• To determine the breaking point, move the probe along the conductive strip of the heater in the appropriate direction. The point where the voltage shown by the voltmeter has changed dramatically is the break point.

Check of the relay of a heater of back glass

• Remove the rear window defroster relay (pic. 19 108).

• Check continuity between relay contacts.

• If the conductivity differs from the required one, replace the relay.

Checking the rear window defroster switch

• Using an ohmmeter, measure the resistance between the contacts of the connector of the heating control unit and the air conditioning system (pic. 19.109).

• If the conductivity is not as specified, replace the switch.

Note. Turn on the rear defroster switch, then check for continuity between tracks 3 and 12 of the connector 9-13 minutes after the switch is turned off.