Test H: Mirrors Do Not Defog Properly
- Ensure gearshift selector in Park. Turn ignition switch to RUN position. Turn rear window defogger on. If rear window defogs or heats up, go to next step. If rear window does not defog or heat up, repair rear window defogger system as necessary. See appropriate REAR WINDOW DEFOGGERS & HEATED MIRRORS - EXPEDITION & NAVIGATOR article.
- Check both outside rearview mirrors, defog operation. If defog function is operating properly, verify customer concern. If defog function is not operating properly, go to next step. .
- Turn ignition switch to LOCK position. Measure resistance between ground and inoperative mirror harness connector terminal No. 3 (Black wire). See Figure. If resistance is 5 ohms or less, replace mirror glass. See SIDE MIRROR GLASS under REMOVAL & INSTALLATION. Recheck system operation. If resistance is more than 5 ohms, repair open in Black wire between mirror and ground. Ground point is located behind left kick panel. See WIRING DIAGRAMS .
- Check defogger switch indicator light with defogger on. If switch does not indicate system is on, go to next step. If switch indicates system is on, repair open in Dark Green/Violet wire between rear window defogger switch, central junction box and outside rear view mirror(s). See WIRING DIAGRAMS . Recheck system operation.
- Turn ignition switch to LOCK position. Check fuse No. 17 (10-amp) in central junction box. If fuse is okay, repair open in central junction box as necessary. If fuse is open, repair short to ground in Dark Green/Violet wire between rear window defogger switch and outside rear view mirror(s). Replace fuse and recheck system operation.