Rear Window & Side Mirrors Do Not Defog
WARNING: This page is about a different car, the 1997 Lincoln Mark VIII and 1997 Lincoln Continental. However, it is still accessible from the selected car via links, so may be relevant.
- Check Indicator
Turn ignition on. Press rear defogger switch. If defogger indicator light does not illuminate, go to next step. If defogger indicator light illuminates, go to step 9). - Check Power To Switch
Turn ignition off. Unplug 5-pin harness connector from rear defogger switch. Measure voltage between rear defogger switch pin No. 2 and ground. See Fig 1 . If battery voltage exists, go to step 5). If battery voltage does not exist, go to next step. - Check Fuse
Remove 40-amp fuse No. 8 (fuse No. 24 on Mark VIII) from power distribution box. Check fuse. If fuse is blown, go to next step. If fuse is okay, repair open Black/Yellow wire (Black wire on Mark VIII) between power distribution box and rear defogger switch. - Check For Short To Ground
Measure resistance between rear defogger switch harness connector pin No. 2 and ground. See Fig 1 . If resistance is greater than 10 k/ohms replace rear defogger switch and retest system. If resistance is less than 10 k/ohms, repair short to ground in Black/Yellow wire (Black wire on Mark VIII) between power distribution box and rear defogger switch. - Check Ignition Power To Switch
Turn ignition off. Unplug 5-pin harness connector from rear defogger switch. Measure voltage between rear defogger switch connector pin No. 3 and ground. See Fig 1 . If battery voltage exists, go to step 8). If battery voltage does not exist, go to next step. - Check Fuse
Remove fuse No. 28 (10-amp) from instrument panel fuse panel. Check fuse. If fuse is blown, go to next step. If fuse is okay, repair open Purple/Orange wire between instrument panel fuse panel and rear defogger switch. - Check For Short To Ground
Measure resistance between rear defogger switch harness connector pin No. 3 and ground. See Fig 1 . If resistance is greater than 10 k/ohms replace rear defogger switch and retest system. If resistance is less than 10 k/ohms, repair short to ground in Purple/Orange wire between power distribution box and rear defogger switch. - Check Ground Circuit
Measure resistance between rear defogger switch harness connector pin No. 4 and ground. See Fig 1 . If resistance is 5 ohms or less, replace rear defogger switch and retest system. If resistance is greater than 5 ohms, repair open Black wire between rear defogger switch and ground. Chassis ground point on Continental is located forward of driver's door. Chassis ground point on Mark VIII is located forward of right door. - Check Power At Fuse No. 30
Remove fuse No. 30 (10-amp) from instrument panel fuse panel. Press rear defogger switch ON. Check for battery voltage at input side of fuse No. 30. If battery voltage exists, go to step 11). If battery voltage does not exist, go to next step. - Check Brown/Light Blue Wire For Open
Turn ignition off. Disconnect rear defogger switch. Measure resistance between rear defogger switch connector pin No. 1 (Brown/Light Blue wire) and Brown/Light Blue wire at hidden antenna module (located in trunk). If resistance is 5 ohms or less, replace rear defogger switch and retest system. If resistance is greater than 5 ohms, repair open Brown/Light Blue wire. - Check Power To Antenna Module
Turn ignition off. Unplug hidden antenna module harness connector. Turn rear defogger switch ON. Measure voltage on Brown/Light Blue wire at hidden antenna module connector. If battery voltage exists, go to next step. If battery voltage does not exist, repair open Brown/Light Blue wire. - Check Antenna Module Ground
Measure resistance between hidden antenna module case and a known good chassis ground. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair module ground. - Check Power To Grid
Reconnect hidden antenna module. Unplug power wire at defogger grid. Turn rear defogger switch ON. Measure voltage between rear defogger grid power wire and chassis ground. If battery voltage exists, go to step 15). If battery voltage does not exist, go to next step. - Check Wires To Grid
Measure resistance of power and ground wires between hidden antenna module and defogger grid. If resistance of either wire is greater than 5 ohms, repair suspect wire. If both wires are okay, replace hidden antenna module and retest system.