electrical problem with my 72

[Tom H.]

I parked my car, running fine. A week later I went to start it and nothing. No interior lights, starter, exterior lights, radio, etc. The horn worked. I checked the battery and it was fine. In looking under the hood, I discovered that a wire coming from the horn relay into a large bundle of wires under the master cylinder had burned in two, and had shorted against the brake line coming from the master cylinder. There are two wires coming out of the bundle that have large hard rubber sleeves,each about 3/8's of an inch thick and 5/8's long, covering the connections. The wire that had burned in half was one of these. I repaired the parted wire and again had lights, radio etc. When I hit the starter, nothing. The second time I turned it, still nothing, but the interior lights went away. The third time I tried the starter, I noticed a tiny wisp of smoke come out of the voltage guage. This happened twice, a wisp of smoke coming from beneath the needle, under the glass.
Any suggestions of what is going wrong would be appreciated.
It's a 350 auto with ac, ps, and pb's. Original dist and wiring. Horn relay replaced about a year ago.
Thanks, Tom

[Jim T.]

Re: electrical problem with my 72

Tom your car does have for sure electical problems. Mayby you should contact the previous owner of the car since he had it for 25 years and see what happened to the car to have the large rubber sleeves on the wire. You need a service manual/wiring diaghram to see what you have left. These cars have several fusable links to prevent burning the wiring up. Makes me wonder is someone replaced the fusable links and connected the wires direct. You may end up with a charred Corvette if it is not repaired correctly. It is very easy to disconnect the battery. Take a 5/8 inch wrench and disconnect the ground cable from the frame and move the cable away from the frame, it is also very easy to reconnect.

[Tom H.]

Re: electrical problem with my 72

Jim, I went and looked at a 71 vette, and it has the same type connections on it. I am pretty sure that my wiring is the original stuff. The owner of the 71 told me that these connections are the fusible links. Could you tell me exactly what to look for as to these? Thanks, Tom

[Jack H.]

If you're talking about horn relay wires....

that connect to the side terminals of the horn relay, that's the engine compartment's B+ bus bar. It's electrically hot all the time and serves as a 'pickup' point for separate engine compartment branch circuits (like heater blower motor, Etc.). Several of the wires that connect here have fusible links built into them which you can see--a cylindrical 'bulge' in the wire about 3-inches back from the terminal on the end of the wire.

The fusible link is how the electrical system protects those branch circuits from electrical overload & subsequent wiring melt-down/damage in the event a given branch circuit shorts to ground when the car is unattended. If this is what's happened (fusible link(s) burned & open circuited to protect the car), it's time to find the source(s) of the short(s), repair them and splice in fresh replacement fusible links....

If you don't feel comfortable doing this kind of electrical troubleshooting, then by all means have the car towed to a competent auto electric shop! If you simply replace the burned out fusible link(s) or wire around them without first finding and fixing the downstream circuit fault(s), you'll either blow the replacement fusible links or run the risk of a MAJOR branch circuit melt-down & electrical fire if you jumper around. Electrical fires on a classic car who's body is flammable fiberglass is NOT a joy to behold!!!!

[Tom H.]

Re: If you're talking about horn relay wires....

Jack, I believe that is exactly what has happened. I am going to get my wiring diagrams and start tracing the wires that come from this area. I appreciate your input, as I have never had any problems in this area, and thus am unfamliar with. I will definatley find the problem before I replace the link, as I can imagine how I would feel if it burned. I am probably lucky that I didn't get a fire while I was looking the first time. I had disconnected the battery while I looked, and reconnected them to try it. Does anyone know where I can find the correct fusible links when I go to replace them?
Thanks again for the info, and if anyone has any ideas on what might commonly happen, or where to look first I would appreciate it.
Thanks, Tom