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Rear Window Does Not Defog

NOTE: Instrument panel fuse panel may also be referred to as fuse junction panel.
  1. Turn ignition off. Inspect METER fuse (10-amp) in instrument panel fuse panel. Inspect DEFOG fuse (30-amp) in engine compartment fuse box. If both fuses are good, go to next step. If fuse(s) is faulty, install new fuse and retest system. If fuse(s) fails again, repair short to ground in Black/Yellow wire and/or Black/Pink wire. See WIRING DIAGRAMS  .
  2. Turn ignition on. Press rear window defogger switch. Rear defogger switch is located in Integrated Control Panel (ICP) in center of dash. If rear window defogger indicator light does not come on and stay on, go to next step. If rear window defogger indicator light comes on and stays on, go to step  14 .
  3. Press rear window defogger switch again. If defogger indicator light does not go off, go to next step. If defogger indicator light goes off, replace warning chime module. See WARNING CHIME MODULE  under REMOVAL & INSTALLATION and retest system.
  4. Turn ignition off. Disconnect Green 3-pin rear window defogger switch harness connector. Rear window defogger switch is located in integrated control panel in center of dash. Press and hold rear window defogger switch. Using an ohmmeter, measure resistance between rear window defogger switch terminals No. 1 and 3 (component side). See Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, replace integrated control panel and retest system. See INTEGRATED CONTROL PANEL (ICP)  under REMOVAL & INSTALLATION.
    Fig 1: Identifying Defogger Switch Connector Terminals
    G98I03540Courtesy of FORD MOTOR CO.
  5. Measure resistance between rear window defogger switch harness connector terminal No. 1 (Black wire) and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in Black wire and retest system.
  6. Remove defogger relay, located in the interior relay panel. Disconnect rear window defogger grid connector, located at rear window. Measure resistance of Black/Blue wire between defogger relay connector terminal No. 87 and grid connector. See Fig 2 . If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in Black/Blue wire and retest system.
    Fig 2: Identifying Defogger Relay Connector Terminals
    G97D28061Courtesy of FORD MOTOR CO.
  7. Perform defogger relay test. See DEFOGGER RELAY TEST  under COMPONENT TESTS. If relay is good, go to next step. If relay is faulty, replace defogger relay and retest system.
  8. Turn ignition on. Using a voltmeter, measure voltage at defogger relay connector terminal No. 86 (Black/Yellow wire). See Fig 2 . If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open in Black/Yellow wire and retest system.
  9. Measure voltage at rear window defogger relay harness connector terminal No. 30 (Black/Pink wire). See Fig 2 . If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open in Black/Pink wire and retest system.
  10. Turn ignition off. Disconnect instrument panel fuse panel 8-pin White harness connector. Measure resistance of Black/Red wire between defogger relay connector terminal No. 85 and instrument panel fuse panel 8-pin White connector terminal No. 4. See Fig 2 and Fig 3 . If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in Black/Red wire and retest system.
  11. Disconnect instrument panel fuse panel 11-pin Green harness connector. Measure resistance of White/Red wire between rear defogger switch harness connector terminal No. 3 and 11-pin Green harness connector terminal No. 1. See Fig 1 and Fig 4 . If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in White/Red wire and retest system.
  12. Disconnect instrument panel fuse panel 16-pin Tan harness connector. Measure resistance between 16-pin Tan connector terminal No. 12 (component side) and 11-pin Green harness connector terminal No. 1. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, replace instrument panel fuse panel and retest system.
  13. Measure resistance between 16-pin Tan connector terminal No. 9 (component side) and 11-pin Green connector terminal No. 4 (component side). See Fig 1 and Fig 5 . If resistance is less than 5 ohms, replace warning chime module. If resistance is greater than 5 ohms, replace instrument panel fuse panel and retest system.
    Fig 3: Identifying Instrument Panel Fuse Panel 8-Pin White Harness Connector Terminals
    G98A03541Courtesy of FORD MOTOR CO.
    Fig 4: Identifying Instrument Panel Fuse Panel 11-Pin Green Harness Connector Terminals
    G98C03542Courtesy of FORD MOTOR CO.
    Fig 5: Identifying Instrument Panel Fuse Panel 16-Pin Tan Harness Connector Terminals
    G98E03543Courtesy of FORD MOTOR CO.
  14. Turn ignition off. Disconnect rear window defogger grid ground connector. Measure resistance of Black wire between rear window defogger grid ground connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair Black wire and retest system.
  15. Disconnect rear window defogger grid power supply connector. Turn ignition on. Press rear window defogger switch. Measure voltage at Black/Blue wire terminal at defogger grid power supply connector. If voltage is greater than 10 volts, repair defogger grid filament. See GRID FILAMENT REPAIR  under ON-VEHICLE SERVICE. If voltage is less than 10 volts, repair open in Black/Blue wire. After repair, retest system.
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