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Control Assembly: Probe

  1. Turn ignition switch to ON position. Turn on and check rear window defogger. If rear window defogger is not working at all, go to next step. If rear window defogger is operating only in some places, go to step 13).
    NOTE: Pay particular attention to wire size. There are Black/Blue (10 gauge) wire and Black/Blue (18 gauge) wire used in this system.
  2. Ensure rear window defogger indicator light is on. If indicator light is on, go to step 6). If indicator light is not on, go to next step.
  3. Ensure fuse is in good condition. If fuse is okay, go to step 4). If fuse is blown, check for shorts to ground in Black/Yellow wire at rear window defogger switch and repair as necessary. Replace fuse.
  4. Ground Black wire at rear window defogger switch. If indicator light comes on, repair Black wire between rear window defogger switch and ground. If indicator light does not come on, go to next step.
  5. Check for battery voltage on Black/Yellow wire at rear window defogger switch connector. See Fig 1 . If battery voltage is present, replace switch. If battery voltage is not present, repair Black/Yellow wire between switch and fuse panel.
  6. Check for battery voltage on Black/Blue (10 gauge) wire. See Fig 1 . If battery voltage is present, go to step 11). If battery voltage is not present, go to next step.
  7. Check rear window defogger circuit breaker. If circuit breaker is tripped, reset circuit breaker. If circuit breaker trips again, check for shorts to ground in Black/White wire at rear window defogger relay. Repair Black/White wire as necessary and reset circuit breaker. If circuit breaker is not tripped, go to next step.
  8. Check for battery voltage on Black/White wire at rear window defogger relay. See Fig 1 . If battery voltage is present, go to next step. If battery voltage is not present, repair Black/White wire between rear window defogger relay and fuse panel.
  9. Check for battery voltage on Black/Yellow wire at rear window defogger relay. If battery voltage is present, go to next step. If battery voltage is not present, repair Black/Yellow wire between rear window defogger relay and fuse panel.
  10. Ground Black/Blue (18 gauge) wire at rear window relay. Check for battery voltage on Black/Blue (10 gauge) wire at rear window defogger relay. If battery voltage is present, repair Black/Blue (18 gauge) wire between rear window defogger relay and rear window defogger switch. If battery voltage is not present, replace rear window defogger relay.
  11. Check for battery voltage on Black/Blue wire at rear window defogger connector. See Fig 1 . If battery voltage is present, go to next step. If battery voltage is not present, repair Black/Blue wire between rear window defogger relay and rear window defogger.
  12. Check for battery voltage on Black wire at rear window defogger connector. See Fig 1 . If battery voltage is present, repair Black wire between rear window defogger and ground. If battery voltage is not present, repair or replace rear window defogger.
  13. Turn rear window defogger switch to ON position. With voltmeter, check center of each filament. If voltmeter reads 6 volts, go to next filament. If voltmeter reads zero or 12 volts, replace or repair filament being measured.
Fig 1: Control Assembly Test Point Locations (Probe)
G90E08201Courtesy of FORD MOTOR CO.
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