65 engine wiring harness short

[Dave K.]

I removed the alternator on my 65 coupe to install #2 and 4 spark plug wires. The alternator and voltage regulator were original and never rebuilt. Upon starting the car, the harness between the alternator and voltage regulator started to glow and smoke. I disconnected the battery cut off switch. Electrical shop reports the alternator were bad. Havig alternator rebuilt and buying a new regulator. I was very careful in reconnecting the alternator and starter wires. Horn relay works. Any comments?DSCN8622.jpgDSCN8625.jpgDSCN8626.jpgDSCN8625.jpg

[Bill B.]

Re: 65 engine wiring harness short

Dave, from an electrical engineer's perspective, if you want to save that original harness instead of replacement, here's what I'd do:

1. Carefully remove the black spiral wrapping from the harness to just beyond the areas of damage
2. Carefully separate each wire in the harness (you may find some insulation fused between a few wires)
3. Carefully inspect each individual wire for damage (exposed conductor, copper loss, etc) If the stranded copper gets excessively heated, the individual copper strands may become brittle and will crack under flex and vibration)
4. If the conductors basically survived, you can individually wrap the compromised wire's insulation with electrical tape to provide electrical insulation to the copper conductor. (don't go crazy - lust a single spiral layer of tape needed to cover.
5. Obtain some repro harness tape (many Corvette parts suppliers have) and skillfully spiral wrap the repaired harness with the new tape. Note the overlap and direction of the undamaged areas of the harness and continue as same.

Do you see a common theme here of "carefully" ?

One note of caution - if the damage goes all the way to the firewall connector, be sure to check the interior side of the connected harness for damage as well. I believe, based on your description that your damage may be limited to the engine harness, but don't know until you check to be sure.

If you feel uncomfortable with performing this task, you may want to seek someone that specializes in such (I'm sure there may be suggestions from members of this discussion board that may offer). If not, you may want to just bite the bullet and replace with a Letric Limited or equiv. offering.

While 12V electrical systems may not appear to be "hazardous", the threat of an engine compartment electrical fire down the road in your vintage '65 Corvette may not be worth over the points being deducted for a replacement harness.

Bill B. - Retired EE

[Dave K.]

Re: 65 engine wiring harness short

Bill,

No intention of reusing the burned harness.
Thanks

[Bill B.]

Re: 65 engine wiring harness short

Ah! Great!! I didn't know if you were seeking comments on repair of such. Good decision!!

B

[Richard M.]

Re: 65 engine wiring harness short

Dave did you remove wires at the horn relay then reinstall? Did you follow the GM wiring diagram? It has a major error.

Rich

[Dave K.]

Re: 65 engine wiring harness short

Richard,

Have not installed yet. Where is the error at the horn relay?

[Richard M.]

Re: 65 engine wiring harness short

See this thread and where I show the errors, in post# 6.

https://www.forums.ncrs.org/showthread.php?119003-melting-power-wire/page2

EDIT- For reference here.... Note this is a 1967 diagram but all 63-67 were wrong in this area. The error shows the 12G Black(Ground) attaching to the 12V buss bar on the horn relay.

Error
HornRelayWireErrorDiagram.jpg

Corrected
HornRelayWireErrorDiagram_Mod.jpg

[Dave K.]

Re: 65 engine wiring harness short

I will be using the Lectric Limited wiring diagram.

Dave

[Richard M.]

Re: 65 engine wiring harness short

I will be using the Lectric Limited wiring diagram.

Dave

Dave can you post a picture of their diagram showing the horn relay and its connections. I recall there was some issue with theirs too, or maybe another vendor's diagram, I forget.

Rich

[Dave K.]

Re: 65 engine wiring harness short

Dave can you post a picture of their diagram showing the horn relay and its connections. I recall there was some issue with theirs too, or maybe another vendor's diagram, I forget.

Rich

Rich,

Will do.

Dave

[Dave K.]

Re: 65 engine wiring harness short

Rich,

LL 65 DiagramHorn1.jpgHorn2.jpg

[Richard M.]

Re: 65 engine wiring harness short

Dave, Thank you.

While I was looking on the LL website waiting for your photo, I was able to partially see their 1965 diagram of the horn relay area. Then I saw your photos. It confirmed what I saw.

They don't even show the Horn Relay mount bolt ground wire from the engine harness, I suspect because theirs is a direct copy of the 1965 AIM wiring diagram.

Here's the '65 AIM Sec12 Sheet D1 wiring diagram. No ground shown. I suppose a good thing.
1965_Sec12_HornRelayx2IR.jpg
Here is AIM Sec12 Sheet A8 showing the Horn Relay mount area and the engine/forward harness ground. That other ground wire ref UPC 6 is the one between the VR and the Relay shown in the above wiring diagram(12B i.e. 12 gauge black)
1965_Sec12_A8_HornRelayMounting.jpg




Here is the above I've modified to include the ground wire for reference.
1965_Sec12_HornRelayModIR.jpg
I never evaluated the AIM errors as much as today so I looked at the earlier AIMs and the errors showed up in 1964, then 1966, then 1967. 1963, 1965 show no error, albeit no ground wire either.

1966(1967 same error but with Fusible Links as shown earlier)
(Note Yellow boxed area is VERY wrong. Causes a direct power to ground short)
1966_Sec12_HornRelayWRONGmod.jpg

1964 and 1963....Strangely, the 1964 has the error while the 1963 is not showing the ground, just like the 1965 diagram.

1964 (Note Yellow boxed area is VERY wrong. Causes a direct power to ground short)
1964_Sec12_HornRelayMod.jpg


1963 No ground shown.
1963_Sec12_HornRelayMod.jpg

Now, with all of this research, I went back to the LL website.

THEIR DIAGRAMS FOR THE 1966 & 1967 are WRONG. They show the same as the AIM Diagrams, a direct power to ground short. Their 1964 diagram is the same as the 1963 in that area, no ground shown.

To All, be extra careful with the wiring diagrams in this area.

Rich




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[Leif A.]

Re: 65 engine wiring harness short

Rich,
I'm not the least bit electrical literate so, kindly, analyze this wiring diagram and tell me what you think about the connections in question.

[Dave K.]

Re: 65 engine wiring harness short

Rich,

At least the AIM shows the ground connecting the alternator and horn relay to the radiator support.
Dave

[Richard M.]

Re: 65 engine wiring harness short

Dave, Yes at least that's a good thing.

Leif, That one looks good, however first glance it looks like it wasn't. Which is that one? Keystone?
PS I got your PM, Thanks.

Rich