Defogger Switch/Timer Relay Module Test
Control switch/timer relay module may be tested in vehicle or on the bench. In vehicle testing follows.
1) Remove switch/timer relay module from instrument panel and leave connector plugged in. See DEFOGGER SWITCH/TIMER RELAY MODULE under REMOVAL & INSTALLATION.
2) Turn ignition ON. Using a voltmeter, check voltage at terminals "B", "I" and "L". See Fig 1 . Terminals "B" and "I" should read 10-14 volts to ground with ON switch pressed. Terminal "L" should show voltage to ground. If Terminals "B" and "I" show no voltage, trace circuit upstream of switch/relay module for any problems (wiring cut, fusible link or circuit breaker blown, bulkhead connector corroded, etc.). If terminal "L" shows voltage, place switch in OFF position. If voltage at "L" remains or indicator light remains on, replace switch/relay module.
3) If switch/timer relay checks out to this point, momentarily operate switch to ON position. Indicator light should come on and remain on for about 10 minutes. Terminal "L" should show voltage. If indicator light fails to light or there is no voltage at terminal "L", replace switch/timer relay. For bench checking switch/timer relay, follow in-vehicle procedure except DO NOT turn ignition ON. With an external DC power supply, apply 12 volts to terminals "B" and "I" and ground terminal "G". See Fig 1 .