Complete Electrical Failure on My '67
Guys, a few weeks ago I went to a local Cruise In driving my '67 Corvette. I had not had it out much since I got it running earlier this year after sitting in my garage for over 21 years. A very good friend of mine helped me to get it running and we also put a new wiring harness in the car. It had been running great till the trip home from the Cruise In. I made a left turn in the sub-division where I live and suddenly everything went dead electric wise. All of the lights went out and the engine went dead. I had a new Optima battery so I hoped that was not the cause. My buddy again came to my rescue. We tried to jump it off to no avail although the battery did spark. We finally loaded it on a trailer and brought it to his shop where he has a hydraulic lift. We checked the wiring connection where the harness plugs into the fuse panel and it was good. We got the car in the air and I checked underneath with my multi-meter to find everything good. We then went back top side where we looked at the ballast resistor and coil to find both good. I did not know how to check the voltage regulator when a female friend of my buddy's came by to pick up some parts. She knew how to check the voltage regulator and found it to be good. She then looked at the horn relay and it sparked when she touched it. I then had interior lights in the '67. As it turns out the massive electrical failure in my '67 was caused by a loose horn relay. A 3/8 box end wrench tightened the bolt holding the horn relay to the radiator support fixing my problem. We all got a laugh that such a small fastener could cause such a massive electrical failure. I hope this experience of mine will help someone else in the future. Happy Motoring! Brooks Glover Jr. (2141)
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Re: Complete Electrical Failure on My '67
Please do yourself a favor and check that ALL the grounds are in place and making good contact. -
Re: Complete Electrical Failure on My '67
Thanks for sharing, Brooks. As Gene mentioned, you may want to check all the grounds. These fiberglass cars can really throw you for an "electrical" loop if they're not grounded correctly...as you have found out. Thanks, again.Leif
'67 Coupe L79, M21, C60, N14, N40, J50, A31, U69, A01, QB1
Top Flight 2017 Lone Star RegionalComment
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Re: Complete Electrical Failure on My '67
Brooks,
I hope you're horn relay issue was the culprit, but that seems unlikely.
If it happens again, open the bulkhead connectors (2) on the left side of the firewall where the wiring harnesses pass through it. The pins in these connectors are notorious for corroding. An occasional careful cleaning with a light coat of dielectric grease after cleaning usually takes care of the problem for a few years.
When corrosion causes these connectors to fail, they do so in exactly the manner that you describe knocking out the whole car, and then sometimes reestablishing connection for no understandable reason. And then they fail again.Comment
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Re: Complete Electrical Failure on My '67
I must agree with Todd. That Ground wire attaches to the Horn Relay mount bolt/radiator support, but it also is connected to the Alternator, which is Grounded via the engine. This then feeds all ground distribution points. If you lost BOTH Grounds, then yes that may cause a electrical open to everything. One of the two.....No. So it may be a good check to check for Ground continuity from engine to alternator also.
You installed new harnesses. Did this include both Main and Forward harnesses?
Todd's comment to check the Bulkhead connectors is a good one. Not long ago I installed both new harnesses in a '67, and 2 Twinlock pins were dislodged in the the Panel. One was the Horn feed as I recall.
It may be possible that the 12G Red 12V feed wire in the Outer Bulkhead Connector may be a intermittent connection. This feeds the entire electrical system. It may be worth a look.
RichComment
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Re: Complete Electrical Failure on My '67
Guys, sorry that I have been out of pocket and have not been able to respond till now. I really appreciate the replies to my post. As I said in my original post a new wiring harness was installed which included the bulkhead connections. This connection was also covered with dielectric grease when it was connected. I am by no means and expert on the electrical systems on these cars but all I know that tightening the small bolt that attaches the horn relay to the radiator support has fixed my problem so far. I am sure it was my fault for not tightening that bolt when the wiring harness was replaced. I still would have never dreamed that this would have caused a total electrical failure. Again I hope that my experience will possibly help one of you if you get into a similar situation. Thanks again! Brooks Glover Jr. (2141)Comment
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Re: Complete Electrical Failure on My '67
Which made me just think of something.
Brooks, while securing the loose Ground wire to the Horn Relay mount tab, you may have inadvertently fixed something else.
The main power feed to the car is sourced at the Horn Relay Buss Bar. There is a Fusible Link at this location, attached in the harness to a large gauge Red wire. It is possible that fusible link is a intermittent connection. It may be just barely making internal contact and may have made contact while tightening the Ground wire. If there was ever a high current draw in the electrical system, this may have compromised the internal copper strands in the link. A simple test of a fusible link is to slightly stretch it from each end. If the rubber insulation stretches it's a sign of a bad link.
Another note. The configuration of the Main Fusible Link at the Horn relay could be different based on time of build. Early cars used a Plug-in removable link, later years were hardwired. There is also another fusible link there which is a smaller gauge which is the feed to the Battery Gauge.
RichComment
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Re: Complete Electrical Failure on My '67
Richard, thanks for your reply to my post. I am not sure about the fusible links in my car. I purchased and installed a new wiring harness from Lectric Limited. I just assume that what they sell is close to or dead on what was on the original harness. All I know is that everything is still working and for me that is good. There may be more gremlins in my system but thus far they have not surfaced. I guess time will tell. Thanks again to all who replied to this post. Brooks Glover Jr. (2141)Comment
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