problem with my 72 lt1... electrical problem

[Mike G.]

i got the 72 lt1 out today because it was a nice day here in atlanta and the car had not been out in several months. the car started right up and ran fine. i drove a couple of miles down the road and stopped for breakfast. when i got back in the car it started right up and then shut down. no lights no horn no nothing, dead. i called a friend to jump me off but that would not work. i pulled the cables off the battery and hooked them directly to the jumper cables and still nothing. i checked to make the wires at the starter were tight and they were. i called a tow and went back inside. when the tow got there i went back outside and the radio was on in the car, with the keys in my pocket. i jumped in and it started right up. i had the tow truck follow me home but it never made it. it went a mile or so down the road and everything went dead again.
what can it be? do i need to get some holy water for the car? its now back in the garage completely dead.

[Kevin G.]

Re: problem with my 72 lt1... electrical problem

Mike,
Very sorry to hear of your troubles. I can not offer any help to you but I experienced the same problem with my LT-1 last season coming home from a show. Just after getting on the car pretty hard about a mile or so later the car just died, nothing not even a tick. After calling my son to my rescue and running home for the trailer I then returned only to have the car start right up. So I loaded it up into the trailer brought the car home and I am still trying trying to figure out the cause? I will watch this thread closely!

[Bob H.]

Re: problem with my 72 lt1... electrical problem

Hi Mike. Have you replaced the battery? I think you have a bad connection internally.

I know you jumped it but I would not depend on that working. You mentioned the radio working later with no keys in it. Is the radio not connected through the ign switch?

If all stock, then it would look like it is in the ignition switch or how about the connector underneath on the column?

Bob

[Rich P.]

Re: problem with my 72 lt1... electrical problem

Just one suggestion. Check the bulkhead connection. This is just under the mastercylinder. I would disconnect it, inspect it, clean, put electrical grease on it and reconnect. Make sure no terminals are working thier way out.

Rich

[Dave S.]

Re: problem with my 72 lt1... electrical problem

Mike,
Very sorry to hear of your troubles. I can not offer any help to you but I experienced the same problem with my LT-1 last season coming home from a show. Just after getting on the car pretty hard about a mile or so later the car just died, nothing not even a tick. After calling my son to my rescue and running home for the trailer I then returned only to have the car start right up. So I loaded it up into the trailer brought the car home and I am still trying trying to figure out the cause? I will watch this thread closely!

Kevin,
I'd look at the ignition coil very hard.

[Thomas P.]

Re: problem with my 72 lt1... electrical problem

.....I think you have a bad connection internally.

I know you jumped it but I would not depend on that working. .....Bob

That is correct, if the battery is "internally" an open circuit, even temporarily, jumping it will probably not work -- depends on the quality of the jumper cables and clamps, most normal jumper cables will not do it.

I had this exact problem in my Ford Ranger and a new battery solved the problem.

But, I also have an electronics background and carry a digital voltmeter in all my cars.
The best advice I can give you is to keep a digital voltmeter handy and, when it happens, check the "terminal voltage" (voltage directly across the battery terminals, not the battery cable connectors) of the battery while someone is trying to start the car.
If the terminal voltage is less than about 10 volts under load, you need a new battery.

Tom Piper

[Rick C.]

Re: problem with my 72 lt1... electrical problem

Mike,

Sorry to hear about your problem. Electrical problems are a pain in the.....

I'm no expert like a lot of these guys, but I've had a lot of electrical problems with my '71 LT1 and experienced problems identical to yours. I'm not totally buying in to the battery idea. The fact that the car started fine twice and then quit while driving leads me away from the battery. Also, your horn not working is an important point. Power from the battery goes directly to the starter and then from the same terminal on the starter goes to the horn relay through a 12/10 guage red wire. If the horn is not working, I'm betting there is a problem in this part of the circuit. One time I had a bad connection at the horn relay due to corrosion, one time the fusible link went bad, and the third time, the connection I had made when I replaced the fusible link became intermittent and opened when it got warm from the current. It sounds to me like a poor connection which fails due to heat or vibration. There should be 12V at the horn relay at all times, whether the ignition switch is on or not.

I also wonder why the radio can be on with the ignition switch off.

Rick

[Paul O.]

Re: problem with my 72 lt1... electrical problem

Mike I would take a hard look at the Negative Battery connection at the frame. If you lose your ground all systems go dead and then a small movement at the connection can make or break your ground. Remember a Corvette is a ground hog you must have good grounds everywhere. Just my thoughts.

Paul 18046

[Patrick H.]

Re: problem with my 72 lt1... electrical problem

I had something similar at the Cincy Regional in 2005 - ground cable of the battery had rotted out.

As above, I'd check the bulkhead connector and battery too.

Patrick

[Mike G.]

Re: problem with my 72 lt1... electrical problem

Mike,

. Power from the battery goes directly to the starter and then from the same terminal on the starter goes to the horn relay through a 12/10 guage red wire. If the horn is not working, I'm betting there is a problem in this part of the circuit. One time I had a bad connection at the horn relay due to corrosion, one time the fusible link went bad, and the third time, the connection I had made when I replaced the fusible link became intermittent and opened when it got warm from the current. It sounds to me like a poor connection which fails due to heat or vibration. There should be 12V at the horn relay at all times, whether the ignition switch is on or not.

Rick

BINGO!!!!!
voltage was getting to the starter and to the horn relay but was not getting to the fuse block. when i played with the wires it would cut on and off. the fusible link between the terminal bolt by the horn relay and the fuse block was bad. as i jiggled the wires it cut on and off. i replaced it and all seems fine now. now i am waiting for another nice day to drive it. i hope this is the last one for a while. my friends call this car my rollback car. it has only been driven 4 or 5 times since restoration and twice it took the ride of shame. it has to do better than that. i built this car as a driver and want to drive it. not much fun with the added stress.

[Paul O.]

Re: problem with my 72 lt1... electrical problem

Mike good to hear you found the problem area and Thank You for posting the problem and what solved it. Many posters post the problem and many members give there input but the poster then does not post the fix. Great help by Rick and all other members.

Paul 18046

[Roy V.]

Re: problem with my 72 lt1... electrical problem

Glad you got it sorted out, I'll have to remember this in case it should ever happen to me.
Regards
Roy