Fried Harness

[Gary C.]

Guys

Would like some opinions on my recent electrical problem. I recently had a total electrical failure on my 67 400HP A/C car. Thought it would most likely be be the usual firewall connector that I have read about here, but found something different.

When I opened the hood I found about 3 or 4 inches of the red altenator wire burned to a crisp up to and including the altenator post and the rubber insulating boot. The altenator post seems to be loose and I think that is my problem. I have sent the altenator to Mr. Pirkle.

Is there a way to check my voltage regulator? This one is a Delco replacement, IIRC it may be solid state.

Can some one who has been there, done that tell me how I might best replace the altenator red wire safely. I like to try to keep original stuff if I can and the only affected wire seems to be the last (or first) three or so inches of the red wire. I have looked at wiring diagrams and it looks like the red wire splices into some other wires on its way to the starter, but it is not clear to me where this occurs or exactly what type of connectors I will encounter or have to replace. I have not unwrapped the harness yet.

If anyone knows where I might find the correct, original type insulating boot I would appreciate that too.

Thanks

Gary

[William C.]

Re: Fried Harness

Gary, you will probably have to untape the harness back to the splice that it attaches to and check for damage to other wires along the way. Hopefully they are ok, If so, it's a matter of FIXING THE SHORT CIRCUIT then follow the fried wire back to the fuse link and replacing the damaged wire. My wiring print is too poor to make out the length, but the splice is located toward the front of dash section of the harness, about 2 inches fron wher the alt branch joins the main harness.

[Edward J.]

Re: Fried Harness

Gary The Red Wire On Alt. Burnt Maybe A Internal Short Of Alt. Where The Post Goes Through Housing. Or A Case Of The Voltage Regulator On All The Time Causing The Red Wire To Over Heat,either Way Rec. Replacing Both Reg.& Reman. Of Alt. When Repairing Harness Make Sure To Use Same Gage Wire As The Factory Installed Soldier The Connection, And Use Heat Srink Wrap On Wire.and Re-tape Harness To Conseal.

[Wayne M.]

Re: Fried Harness

Gary --did this just happen out of the blue, or had you had work done on the car (new alternator or volt reg) ? Frankly, I'm surprised that with all the fusible links added to the 1967 model year cars (5 on standard Corvette wiring systems; maybe more with A/C cars) that anything could "fry".

[Gary C.]

Re: Fried Harness

Thanks for the replies guys. The car gave me a few "warning signs" as it cut out a few times prior to the last straw. I thought it was probably a intermittent non contact at the firewall red wire connector. I was surprised to find the burned alt wire. I unwrapped the harness this evening. The wire is indeed only burned for 3 or 4 inches extending from the alternator lug, which was burned so badly it crumbled into pieces. The adjacent wires appear unaffected. The splice for the red wire is just prior to the alternator branch point of the harness. The spice connector is a crimp on bugger that allows the single red wire to become 4 wires. Does not look like something I will easily find a replacement for. If anyone knows of a source for this type of connector, let me know.

I replaced the voltage regulator about a year ago, I am increasingly uncomfortable with replacement parts, and I am not positive the voltage regular had no role in this failure. After assessing everything it does seem the terminal post in the alternator somehow became loose and shorted out, but again I connot be sure the voltage regulator caused some problem to lead to this. I would like to know if there is a way to "test" my voltage regulator. If someone is familiar with todays replacement voltage regulators and knows them to be bulletproof or imported junk, please share with me.

I have not tested the fusible links in the voltage regulator wires, but will do so. Visually they look ok.

[Terry M.]

Re: Fried Harness

"After assessing everything it does seem the terminal post in the alternator somehow became loose and shorted out, but again I connot be sure the voltage regulator caused some problem to lead to this."

You may be on to something here. IF the terminal at the alternator became loose -- either at the screw connection to the alternator OR at the crimp to the wire -- under a heavy load the heat at the connector would travel up the copper wire (remember copper is a good thermal conductor) and cause the kind of damage to the connector and wire you have described. Loose connections can develop a lot of heat as the electrical current tries to pass through. This heat will rapidly corrode the ring terminal and make the electrical contact worse.

Your problem may have started as simply as a loose connection.

[Joe L.]

Re: Fried Harness

"After assessing everything it does seem the terminal post in the alternator somehow became loose and shorted out, but again I connot be sure the voltage regulator caused some problem to lead to this."

You may be on to something here. IF the terminal at the alternator became loose -- either at the screw connection to the alternator OR at the crimp to the wire -- under a heavy load the heat at the connector would travel up the copper wire (remember copper is a good thermal conductor) and cause the kind of damage to the connector and wire you have described. Loose connections can develop a lot of heat as the electrical current tries to pass through. This heat will rapidly corrode the ring terminal and make the electrical contact worse.

Your problem may have started as simply as a loose connection.

Terry and Gary-----


I agree. Considering what's happened and what's NOT happened, I think that the root cause may have been just a loose connection.

I don't recall how to test these external voltage regulators. However, I think there is a pretty detailed description of such testing found in the Chevrolet Chassis Service Manual. As I recall, it's not too difficult and requires only a VOM meter.

I don't think you'll have a solid state or transistorized type regulator. Those were used on a few Corvettes, but I think it was limited to the 1965 model year and, possibly, 1966. I don't think that any 1967's got them. It's easy to tell. If you have a "squarish" box with a black painted cover, then you have the standard mechanical type regulator. The solid state type used an unpainted aluminum housing.

[Terry M.]

Re: Fried Harness

Joe, were not some of the SERVICE voltage regulators electronic? I thought I had heard that from someone, but separate voltage regulators are way outside my field.

We used to have a alternator/voltage regulator tester in school, but about five years ago it found its way to Masters City. I can picture the illustrations in the Chassis Service Manual, though. I'm sure the testing instructions are there.

[Joe L.]

Re: Fried Harness

Joe, were not some of the SERVICE voltage regulators electronic? I thought I had heard that from someone, but separate voltage regulators are way outside my field.

We used to have a alternator/voltage regulator tester in school, but about five years ago it found its way to Masters City. I can picture the illustrations in the Chassis Service Manual, though. I'm sure the testing instructions are there.

Terry-----


As far as I know, all of the SERVICE regulators for 1955-68 Corvettes were conventional mechanical type regulators. However, I believe there was once available in SERVICE from Delco a retrofit KIT to convert a vehicle with a conventional mechanical regulator to an "electronic" unit. Vaguely, I recall that these units were something like half mechanical and half electronic. I believe the regulator unit which came with the kit was the same as or similar to those used on a very limited number of 1965 Corvettes with C-60, K-66 and high amp output alternators.

I have also seen these units on some older light aircraft applications. I believe they were retrofit for those applications, too.

[Terry M.]

Re: Fried Harness

I knew I should have stayed out of these mid-year discussions.

I was pretty sure of the connection failure mode though. We see it all too regularly in the electric utility industry. There is a reason we use stainless steel hardware and silver plated copper terminals -- oh, and we torque the fasteners with a torque wrench too. There is no substitute for a good, clean and tight connection if it is to carry the rated current for any length of time.

[Jack H.]

Re: Fried Harness

Sometimes maintaining factory originality on items that have 40-50 years of age on them, isn't always the best move! Wiring components DO age over time especially considering underhood temperatures that 'cook' the insulation. You can wind up with insulation that's no longer soft/supple and oxidation at points of contact (crimp, splice) that raise the ohmic contact profile of these contacts...

On testing an external voltage regulator, the info given in Chevy service manuals is basically a 'go/no-go' approach. Most competent auto electric shops will have a commercial bench tester that dynamically exercises the voltage regulator allowing its cut-in/cut-out profile to be adjusted to compensate for normal contact point wear.

Essentially, you 'dial in' the number of the voltage regulator, attach it to the tester and the tester simulates the rest of the car's charging system under 'live' operation. I feel more comfortable with that kind of exercise/analysis than a one shot, go/no-go test...

[John D.]

Re: Fried Harness

Jack, I agree with you on retaining 40-50 yr old wiring. I would say a fellow is living dangerously using antique wiring. Sorta like an old farm house I own that has a combo of knob and tube and modern wiring. Some day it may go up in smoke.
My 63 is loaded with NOS parts but the wiring is new repro. I will never forget when my other 63 caught fire. The original dash wiring harness and engine wiring harness went up in smoke taking some of the car with it. Luckily I had one of those green knobs on the battery but by the time I got my fat butt out of the car-and over to the battery several thousand dollars of damage was done. No I would go for a nice new wiring harness. It's a matter of safety. But that is just my opinion. Plan B would be to look for an over the counter GM replacement harness. JD

[Jack H.]

Re: Fried Harness

The inside rear cover of my copy of the 11/64 edition of the Delco Remy Delcotron catalog touts the "New All-Transistor Voltage Regulator" repleat with a conversion chart listing prior/existing DR electromechanical V-regs and their functional transistorized, drop-in, replacements...