Electrical Problem with my 1962 Corvette

[John O.]

Ok guys, I really need your help. I did a total 100% frame off restoration on my 62 corvette that I finished back in 2006. Here is the problem that started 2 years ago. I did not drive the car much because of this. While driving the car, at different times the engine sounds like it shuts off & on in a split second. I parked the car in the garage with the head lights on & engine running at idle. As I sat in the car the engine and the lights would shut off & on in a split second. I noticed the ammeter went all the way down to the negative side then back up to near zero. I replaced the Ignition Switch, Starter Solenoid, Voltage Regulator, Coil, no luck. There is a 12 gauge wire that feeds from the starter solenoid to the ammeter. I by passed that by running a 12 gauge wire from the Battery directly to the wires on the other side of the ammeter thinking maybe the old wire or ammeter was at fault. No luck.I checked out the Battery and the Generator at a shop and they checked out good. I cleaned the grounds on top of the engine.Are there any other grounds i'm not seeing that could be causing this? Any help would be greatly appreciated. I want to enjoy my vette again. You may also email me at clasvette@aol.com

Thanks for all your answers in advance.....John

[Philip A.]

Re: Electrical Problem with my 1962 Corvette

Start checking the distributor. The ground wire may have chaffing. The intermittent nature could be caused by this issue combined with the distributor advance moving the wire. Check the post "no fire in the hole"

[Bill W.]

Re: Electrical Problem with my 1962 Corvette

Check the plugins at the fire wall to interior block

[John O.]

Re: Electrical Problem with my 1962 Corvette

Check the plugins at the fire wall to interior block

Thanks for the response Phil and Bill. I'll check the wire again on the Distributor. It was a new wire, but remember what I said, it shut my Headlights off and on quickly. Since the headlights turn on with the key off, I figured it might be more. But I will check that wire again.

Bill, are you talking about the wires going right into the fuse block? If you are then i'll have to pull the fuse block. That was one thing I did not check. Also the wire harness is new from Lectric Limited.

Thanks again, any other ideas are appreciated.

John

[Bill W.]

Re: Electrical Problem with my 1962 Corvette

John my 62 lost power when I hit a bump one time .I got out and wiggled the wires at the fuse block & it was fine . I have seen this happen on a couple of C2s also .

[John O.]

Re: Electrical Problem with my 1962 Corvette

Ok Bill thanks. I'll give it a shot. I have nothing to lose. Thank you again

[Mike E.]

Re: Electrical Problem with my 1962 Corvette

The 62 I've had since 1977 gave me similar major headaches back in the mid-80's. Turned out that inside the plastic plug at the back of the ignition switch, one of the contacts was making intermittent contact. I carefully extricated, cleaned, bent the retaining tab ever so slightly, used dielectric grease, and reinserted. No problems since.

[John O.]

Re: Electrical Problem with my 1962 Corvette

Thanks Mike, now that I think of it, that plug did not feel real tight. I'll try that also.

[Roger W.]

Re: Electrical Problem with my 1962 Corvette

How about a loose post on the battery?

[John O.]

Re: Electrical Problem with my 1962 Corvette

Hi Roger. I cleaned and tighten the battery posts real good. I'm going to try tightening the contacts on the center plug on the ignition switch first as Mike Ernst suggested as soon as I get some time. But thanks for the suggestion

[Richard M.]

Re: Electrical Problem with my 1962 Corvette

As I sat in the car the engine and the lights would shut off & on in a split second.

I noticed the ammeter went all the way down to the negative side then back up to near zero.


John, I think this is the major clue to your problem. When the ammeter pegs negative, this is telling me you have a direct short in the main 12volt circuit to Ground, but intermittently. Because it's intermittent, it is difficult to diagnose.

One of the most common faults is a short of the Brown wire Ignition circuit through the ballast resistor to the coil+. The output side of the ballast is typically a green wire to coil+. If the Green wire briefly shorts to ground, this could cause a intermittent failure. The most common short that can occur here is when the Green wire gets rubbed against the distributor ignition shield. First check your Green (coil +) wire to make sure it is not rubbing ground anywhere.

If that is alright, then you have to go deeper. However, you need a "unpowered" test method to try to find it. This will reduce risk of burning your new harness or other electrical items, or even the car itself. Because there is no main circuit protection in these cars there is high risk that a direct power to ground short could be detrimental.

The way I would start a diagnosis is this......

1 - Disconnect Battery Plus and Ground cables.

2 - Connect a ohmmeter to both battery cables. You will get a low reading, maybe only a few ohms, as all live paths will still be connected.

3 - With a helper, or by using long leads on the meter, move around to these locations and wiggle the wiring at these locations. If you see a major change of value in your meter reading towards zero, that may be the area which is suspect of the short circuit.

4 - Edit......I forgot this step in my initial post. Turn the Ignition key to RUN. In your testing you can also test it OFF, but ensure you do it ON.

a - Main fuse panel wire bundle. Ground is not directly connected inside the fuse panel, but the main ground wire is inside the bundle. It's the 12G Black/White stripe wire.

b - Underdash harness

c - Engine harness at the ammeter and the ignition switch. Grab the wires at the ammeter lugs and wiggle all of them around. The ammeter could have a intermittent short between the input/output lugs and the case. The small gauge cases and entire metal instrument cluster is ground.

d - Horn relay wiring. Also wiggle the horn relay cover.

e - Clock harness and lighter harness

f - Instrument cluster Pink wires at the rear of the small gauges.

g - Voltage Regulator wiring and the generator harness.

h - Headlight switch feed (Red wire)

i - Ignition Switch Red wire area.


Below is a crude diagram of the "unprotected" circuit path in these cars. You can see all of the items connected directly to battery power at all times, even with Key off.

C1batmod.jpg

I'd try this unpowered test to help find it before any more powered tests are performed. You may have a bad harness or gauge or other intermittent short going on. These are the tough ones to find but with some tedious testing it may help show the fault.

Rich

[Ed S.]

Re: Electrical Problem with my 1962 Corvette

Richard,
Your explanation and advice, along with the diagram showing items connected to battery power at all times are all very good reasons to have a battery shut off switch on early generation Corvettes, and.... be sure to use it when the car is not in use or unattended. It's bad enough that someone's classic Corvette might self destruct without warning but it would be a shame if it took a home along with it and possibly worse.

[Richard M.]

Re: Electrical Problem with my 1962 Corvette

Hi Ed,

Yes I've had a battery cutoff on my '59 forever. Always a good idea. I'm also a proponent of adding circuit protection for several of those other unprotected areas prone to potential hazards. I've come up with a method to add fuses to various spots of "interest" which can be removed for those that want to be judged at some future time.

Here is a method I use for the Ignition Circuit.

http://home.comcast.net/~richmz/site/?/page/1956_to_1962_Corvette_Ignition_Fuse/

Attached is a pdf version with additional info that Frank D, Dave Z and I published a while ago. Dave is the PDF creation expert.

Similar methods can be used for other circuits like the clock and lighter.

Rich

[Jerry K.]

Re: Electrical Problem with my 1962 Corvette

Try removing the ignition shielding and see if the wire from the wiring harness that connect to the coil shorts out on the shielding top. I've had to rotate the coil enough to make clearance. The problem you described is what I've experienced.

[Roger W.]

Re: Electrical Problem with my 1962 Corvette

John, I did not mean the clamps connecting to the battery posts. I had a 63 Chevy 409 years ago that had a battery with a loose Positive post. If the post was wiggled, there was an intermittent open internal battery connection. Of course today the batteries are constructed much better than back in the 60's.