77 electrical issue...help...
Thread Starter
Intermediate
Joined: Jun 2012
Posts: 31
Likes: 0
From: Braintree MA
77 electrical issue...help...
Having an issue with my 77. When driving at night, everything is fine, then for no reason the speedo and tach pannel lights go out, the high beam indicator comes on and the two directional lights come on solid. The rest of the gauges are unaffected, no issues with those at all. Then just as it happened for no reason, everything goes back to normal. This first happened a week ago and went away. then tonight while driving though town they went out again, drove down a few blocks, while waiting at a stoplight, they came back on again. went on and off a few times and now finally off and wont come back. the tach and speedo still both work, its just the lights that dont. here is a pictures of what it is doing. any ideas? anyone run into this before?
I'm thinking this must be a ground issue, but have no idea where to start. Checked the fuses and all are good. (besides if it were a fuse all of the panel lights would go out) I saw someone else here having a similar issue but with it only affecting his speedometer, with the light going out and the high beam indicator and left turn signal coming on.
here is the older post, where a similar issue came up.
http://forums.corvetteforum.com/c3-g...or-closes.html
I'm thinking this must be a ground issue, but have no idea where to start. Checked the fuses and all are good. (besides if it were a fuse all of the panel lights would go out) I saw someone else here having a similar issue but with it only affecting his speedometer, with the light going out and the high beam indicator and left turn signal coming on.
here is the older post, where a similar issue came up.
http://forums.corvetteforum.com/c3-g...or-closes.html
Last edited by 1977c3; Jun 29, 2012 at 08:36 AM.
Thread Starter
Intermediate
Joined: Jun 2012
Posts: 31
Likes: 0
From: Braintree MA
Thanks for the wiring diagram, much more detailed than the ones I have. I start with the grounds. My guess based on this diagram would be to start at the drivers door hinge and see if there are any obvious issues with the ground there.
Melting Slicks
Joined: Feb 2007
Posts: 2,709
Likes: 269
From: S.E. MI
St. Jude Donor '15
It is from a Chevy dealer electrical manual. I bought one on Ebay.
This site has the whole 77 electrical manual.
http://www.europeancorvette.com/html...l_diagrams.htm
This site has the whole 77 electrical manual.
http://www.europeancorvette.com/html...l_diagrams.htm
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Certainly the ground. When you lose the ground, the electricity finds the next path which is through the high beam and turn lights. I would look at the printed circuit and look at the main plug to the board. It is common for the fingers on the wiring circuit to get pulled up from the printed circuit board.
Thread Starter
Intermediate
Joined: Jun 2012
Posts: 31
Likes: 0
From: Braintree MA
still having issues. All grounds seem good. Its completely random. Driving tonight I drove for about a hour no problem, then it went back and forth several times within 15 minutes. Then out completely, I pulled into my driveway still not working. let the car just idle there and they came back on for a few minutes and then back out again.
Instructor
Joined: Oct 2008
Posts: 176
Likes: 1
All of these grounds tie together inside the harness. Time has caused the solder to separate. Find where joint, is (lump under harness tape) open tape and resolder it should fix issue,, or spend $500 on new dash harness.
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Thread Starter
Intermediate
Joined: Jun 2012
Posts: 31
Likes: 0
From: Braintree MA
Would this be located in the general vicinity of the grounds at the door hinge?
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Check the braided ground under the "a" pillar from the frame to the birdcage.
Check all with an ohm meter and best just to redo the connections adding some anitseize.