In-Vehicle Testing
- Remove control panel from instrument panel without disconnecting electrical connectors. See CONTROL SWITCH/TIMER RELAY MODULE under REMOVAL & INSTALLATION.
- Turn ignition on. Using a voltmeter connected to ground, backprobe control switch/timer relay module connector terminals No. 1 (Black/Red wire) and No. 2 (White wire). See Fig 1. If battery voltage exists, go to next step. If battery voltage does not exist, inspect fuse No. 7 (10-amp) in fuse block located under left side of instrument panel and maxi-fuse No. 10 (40-amp) in Power Distribution Center (PDC) located in engine compartment, next to battery. If fuses are okay, go to next step. If either fuse is blown, inspect and repair suspect short circuit. See WIRING DIAGRAMS . Replace fuse.
- Turn defogger on. Using voltmeter, backprobe control switch/timer relay module connector terminal No. 5. Battery voltage should exist. Turn defogger off. Voltage should not exist. If voltage is as specified, go to next step. If voltage is not as specified, replace control panel. See CONTROL SWITCH/TIMER RELAY MODULE under REMOVAL & INSTALLATION.
- Turn defogger on. Indicator light should illuminate and remain on 8-10 minutes. If indicator fails to operate as specified, replace control panel. See CONTROL SWITCH/TIMER RELAY MODULE under REMOVAL & INSTALLATION.
Courtesy of DAIMLERCHRYSLER CORP.