Defogger Control Switch/Timer Relay Test

1. Remove control switch/timer relay from instrument panel with wiring still connected. See appropriate INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIP Section. Turn ignition on. Using a voltmeter, check for voltage at terminals "B", "I" and "L". See Fig 1 and Fig 2 . Terminals "B" and "I" should have 10-14 volts. Terminal "L" should have zero volts.
2. If terminals "B" and "I" read zero volts, check circuit for defective wiring, blown fusible link, open circuit breaker or loose connection at bulkhead connector. If terminal "L" reads greater than zero volts, ensure control switch is in OFF position. If voltage still exists at terminal "L" or indicator light remains on, replace control switch/timer relay.
3. If control switch/timer relay voltage readings are okay, move control switch to the ON position. Voltage should exist at terminal "L" for about 10 minutes and indicator light should be on. If light is off or no voltage exists at terminal "L", replace control switch/timer relay.

Fig 1: Identifying Control Switch/Timer Relay Terminals

Courtesy of CHRYSLER MOTORS.

Fig 2: Rear Defogger Electrical Circuit

Courtesy of CHRYSLER MOTORS.