Rear window defroster (Mitsubishi Space Star)

Defrosting of the rear window is carried out by a heater, which is a series of parallel conductors sprayed onto the glass. When electric current is passed through, 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 equipment unit.

Examination

• Start the engine and let it run at 2000 rpm.
• Turn on the rear window defroster. Connect the negative probe of the voltmeter to the vehicle ground. Connect the voltmeter probe to the center of each conductive strip of the rear window defroster in turn (Fig. 19.107). The voltmeter should show a voltage of about 6 V.

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

Checking the rear window defroster relay

• Remove the rear window heater relay (Fig. 19 108).

• Check the conductivity between the relay contacts.

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

Checking the rear window defroster switch

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

• If the conductivity is different from the required value, replace the switch.

Note: Turn on the rear window defogger switch, then check for continuity between pins 3 and 12 of the connector 9-13 minutes after turning off the switch.