Rear Window Defogger Fan: Testing

Check that all in-line fuses or circuit breakers are operational and supply power. Measure voltage at motor, if no voltage is present check wiring harness and control switch. If motor runs at some speeds, but not at others, check speed control resistors.

Fig 1: Wiring Diagram of Rear Window Defogger Fan Circuit with Resistor or Resistance Wire in Circuit

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Fig 2: Component Layout of Rear Window Defogger Fan System (Ford Motor Co. Shown)

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