Help! Defroster Not Working on 81

[alyevich]

New owner in need of help. Spent a good time driving it and now I want to start repairing lot of little things. Currently waiting for shop manual to arrive by mail.
The rear defroster does not currently work. The switch does not click into any position when moving it forward or backwards. Nor does an indicator light activate on the switch itself (it looks like there is a small light on the top of the switch which I imagine would turn on when the defroster is on).
Where should I start? Is it likely the switch is dead? A fuse that needs replaced? etc
Any help would be appreciated.
Thanks,
Al

 

[Evolution1980]

It's not uncommon for the fuse to pop.
The switches themselves can get flaky also. A year or two ago, mine just stopped working. A month or two later, it was working again!
When it's all working you should hear the faint click under the dash when it turns on and it should light up.

 

[AGVI]

Those things suck up a lot of juice!

 

[alyevich]

OK....does that have any hidden meaning or something? Do you mean that it's common for the fuse to blow?
Al

 

[bill81vette]

there is a small lite bulb inside the switch that does lite when it is switched on...the bulb could either be blown or your switch is not working at all....
Do you have a factory service manual, and an AIM...assembly instruction manual...these are the bibles to repairing our vettes...
I'll have to check but there is a procedure to check the switch to see if it is bad or not...

 

[Vette79]

For me it was a bad ground which is very common on C3's. Just clean them up.

 

[LVMYVT76]

Can you check for 12 volt dc where the rear defrost plugs together with the switch turned on? Get a good ground and use a volt meter or a test light to check for 12 volts, no 12 volts check at switch for 12 volts, no 12 volts need to check further back, etc. Don't have a test light or meter? BUY one, there under $10.00 usually. They are worth their weight in gold! You can do so much with them!

 

[Vette79]

Can you check for 12 volt dc where the rear defrost plugs together with the switch turned on? Get a good ground and use a volt meter or a test light to check for 12 volts, no 12 volts check at switch for 12 volts, no 12 volts need to check further back, etc. Don't have a test light or meter? BUY one, there under $10.00 usually. They are worth their weight in gold! You can do so much with them!

Good call. My first electrical issue was the rear defroster. The test light is a great tool.

 

[Mr. Chuck]

New owner in need of help. Spent a good time driving it and now I want to start repairing lot of little things. Currently waiting for shop manual to arrive by mail.
The rear defroster does not currently work. The switch does not click into any position when moving it forward or backwards. Nor does an indicator light activate on the switch itself (it looks like there is a small light on the top of the switch which I imagine would turn on when the defroster is on).
Where should I start? Is it likely the switch is dead? A fuse that needs replaced? etc
Any help would be appreciated.
Thanks,
Al

My 81 defogger will require that you hold the switch in the on position before the "ON" light comes on. If you try it more than once, the electronic timer part of the circuit may cause it to not turn on right away, the reason you may have hold it in the on position.
Also note as stated in a prior reply, the defogger draws a lot of current and as such, at engine idle speed the amp meter may drop to 12 - 13V; well below normal output voltage of ~14 Volts, especially if you have the wipers going and the radio on.