I have '79 vette with a rear defogger not working. The green light on the switch switch does not come on. I looked under the dash at the fuse panel but am unable to locate the fuse for this. The manual says it is a 35 amp fuse but I can't find it.

Any ideas?

My 81 Shop Manual says that I would have a "10 amp fuse and a circuit breaker located in the fuse block"  Based on what you are saying, it could also be:  Circuit breaker open from an electrical short in the power feed circuit, Burned fusible link, Burned out or missing monitor lamp, Open circuit in either of the wiring harnesses, Inoperative or disconnected control timer assembly, Defective control switch, Defective control switch, Defective control timer switch, Defective control timer switch.  Any further questions???  I am going to go out on a limb and say that you have a defective control timer.  It should be located in the center consoul or in the compartments behind the seats!!  Let me know what you discover!!   There is a 30 amp circuit breaker and a 10 amp fuse in the fuse panel (should be near the drivers left food behind the left kick panel!  dskopp2011-05-09 16:18:38

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Jim, when my rear window defroster went out, I replaced the switch AND the relay and it still didn't work. Turned out the problem was where the harness in the engine compartment goes into the bak of the fuse box. It had pulled away and corroded. Fixed that and it was good as new (not typical results, your results may vary. Any problems contact your doctor. Oh wait, thats different!)

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I'll take an electrical tester through the components that are outlined above this weekend and see if I have any luck.