Frying Headlights in 1980
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Frying Headlights in 1980
My '80 is putting out way to much voltage for the headlamp circuit and cooking front lights like flashbulbs. When I put a volt meter on the yellow wire coming from the headlamp switch I get close to 50 volts which is frying the headlights. The relay in the switch is obviously resetting itself after the blow. Also, there appears to be good continuity between the tan, green and black lines feeding the front headlamps and the under dash feed. Please note that I have a good 12 to 14 volts elsewhere in the car including the parking and turn signal circuits. I have a 1980 wiring diagram but am still at a loss.
FYI this is a rebuild effort coming from a car parked for about 3 years in an Alabama field that prior to being parked was subject to multiple bubba repairs.
Any help on this matter would be greatly appreciated.
FYI this is a rebuild effort coming from a car parked for about 3 years in an Alabama field that prior to being parked was subject to multiple bubba repairs.
Any help on this matter would be greatly appreciated.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
50 volts at the headlights?
Verify what you have at the alternator with it running and at the battery.
At the headlight connector check from each pin to a good ground.
Verify the grounds in the front end, they end up on the radiator support I believe.
Verify what you have at the alternator with it running and at the battery.
At the headlight connector check from each pin to a good ground.
Verify the grounds in the front end, they end up on the radiator support I believe.
Racer
Joined: Nov 2006
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From: Tampa Bay Area, U.S.A. (Zombie Nation)
If you are getting the correct 12-14 volts everywhere else then I'd start looking for where Bubba has installed some sort of voltage multiplier or converter circuitry. For what exact purpose who knows. Your alternator just doesn't output multiple or "various" voltages. It's either one or the other (correct or not correct). Afterall, there's only one output terminal on a standard alternator.
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Thanks for the suggestions. I pulled the alternator and it checked good at O'Reilly's. One of the problems is that I have a number of cut wires roaming about the port side of the engine bay and I can't seem to find a clear picture of exactly which wires go onto the alternator. I have the big black ground figured out and the smaller tan and red to 1 and 2. However, I have a smaller black that looks like it goes on the red post. Then, there is a stray heavy red wire that had been cut that may or may not need to join the smaller black. Does anyone have a picture of a 1980 alternator correctly wired?
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Thanks for the suggestions. I pulled the alternator and it checked good at O'Reilly's. One of the problems is that I have a number of cut wires roaming about the port side of the engine bay and I can't seem to find a clear picture of exactly which wires go onto the alternator. I have the big black ground figured out and the smaller tan and red to 1 and 2. However, I have a smaller black that looks like it goes on the red post. Then, there is a stray heavy red wire that had been cut that may or may not need to join the smaller black. Does anyone have a picture of a 1980 alternator correctly wired?
http://forums.corvetteforum.com/c3-g...or-anyone.html
Scott
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Joined: May 2006
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From: Dayton, Ohio
I have the big black ground figured out and the smaller tan and red to 1 and 2. However, I have a smaller black that looks like it goes on the red post. Then, there is a stray heavy red wire that had been cut that may or may not need to join the smaller black. Does anyone have a picture of a 1980 alternator correctly wired?
The small black is most likely the ground for the headlights and should go with the large black to the alternator case.
The heavy red that was cut might be the battery charge wire if your car had the optional radio that required it.
Here is a link to a 78 diagram which is the same as an 80 minus the optional "charge wire".
http://www.corvetteforum.net/c3/tune...l/index8.shtml
Burning Brakes
Joined: Apr 2007
Posts: 1,028
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From: SOUTH ELGIN IL
You should try to find one of these diagrams for your year:
http://docrebuild.com/oosoez.html
I got these very ones for my '74 and they are the best, much better than any AIM I've seen will show. Not only are they an accurate wiring diagram but they also show the color of the stock wires and also the shapes of the connectors. I use mine all the time, both inside and outside diagrams. Not sure why they stop at '77, my guess is development time is still needed to round out the C3's. Maybe you could give them a call, or maybe wait for the '78's and they would work for you. The only problem with these is that they don't show you how to install or diagnose aftermarket systems but hey, you can't have it all and that's what the Forum is for!
50V seems way out of line. You should be able to find something somewhere that shouldn't be in the circuit I would think- like a hamster running on a wheel
http://docrebuild.com/oosoez.html
I got these very ones for my '74 and they are the best, much better than any AIM I've seen will show. Not only are they an accurate wiring diagram but they also show the color of the stock wires and also the shapes of the connectors. I use mine all the time, both inside and outside diagrams. Not sure why they stop at '77, my guess is development time is still needed to round out the C3's. Maybe you could give them a call, or maybe wait for the '78's and they would work for you. The only problem with these is that they don't show you how to install or diagnose aftermarket systems but hey, you can't have it all and that's what the Forum is for!
50V seems way out of line. You should be able to find something somewhere that shouldn't be in the circuit I would think- like a hamster running on a wheel
Last edited by Dantana; Jul 21, 2011 at 07:15 PM.
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I think I may have things under control and thanks to all. In summary, there are 5 wires that hook up to the alternator. A big black to the base ground. A small black which actually was spliced in by the factory that feeds off of a red (confirmed at 13.5 volts when the engine is running as a positive) from the starter that goes on the red batt post, a big red with a fuse link that is a straight shot to the battery that also goes on the red battery post, and a brown and another red that go on 1 and 2. Bubba had cut the red wires when he dropped an 84 block in and had in correctly reconnected the red wires and swapped them with a frog connector on the battery lead putting it in the 1 position. The upshot was that the circuitry was doing somesort of exotic feedback loop dramatically increasing the voltage via the diodes in the alternator. At one time I probably could have done the math.
Bad things happened when Bubba had to go away, courtesy of the state, for six to nine months.
Bad things happened when Bubba had to go away, courtesy of the state, for six to nine months.
