Rear Defogger: Description and Operation

The rear window defogger system is controlled by the time control unit. The rear window defogger operates only for approximately 15 minutes.
Power is supplied at all times
^ to rear window defogger relay terminal (3)
^ through 20 A fuse (No. (1), located in the fuse block) and
^ to rear window defogger relay terminal (6)
^ through 20 A fuse (No. (2), located in the fuse block).
With the ignition switch in the ON or START position, power is supplied
^ to the rear window defogger relay terminal (1).
Ground is supplied to terminal (2) of the rear window defogger switch through body grounds (M51), (M76) and (M77).
When the rear window defogger switch is activated, ground is supplied
^ through terminal (1) of the rear window defogger switch
^ to time control unit terminal (3).
Terminal (12) of the time control unit then supplies ground to the rear window defogger relay terminal (2).
With power and ground supplied, the rear window defogger relay is energized.
Power is supplied
^ through terminals (5) and (7) of the rear window defogger relay
^ to condenser terminal (1)
^ through terminal (2) of the condenser
^ to the rear window defogger.
The rear window defogger has an independent ground.
With power and ground supplied, the rear window defogger filaments heat and defog the rear window.
When the system is activated, the rear window defogger indicator illuminates in the combination meter.
Power is supplied
^ to terminal (29) of the combination meter
^ from terminal (5) of the rear window defogger relay.
Terminal (27) of the combination meter is grounded through body grounds (M51), (M76) and (M77).