melting power wire.

[Joseph R.]

Re: melting power wire.

Just saw your post. I burned another front harness last week. I pulled it all out and reconnected. Also bought a new horn relay. Turned battery on and the front part is ok but it started to heat up around the fuse connector box on the firewall. All other wires are cool. Fortunately juice was going in for just a second so nothing melted. Since this another ground fault it must be an unfused wire. I think wire to ammeter is unfused so I have to check that and then keep looking. I had it running and driving but I was playing with horn relay again and that is when I burned out harness near that relay. . I also put in the drivers side of air con and I may have screwed things up there. Never a dull moment. Any other thoughts would be appreciated. Also taking an online course on electrical wiring in cars

[Joseph R.]

Re: melting power wire.

Also reviewing this treatise on cluster wiring by Dave zuberer. He references rich Mozzetta. Rich was helpful and I wonder if he has any thoughts. This has to be another direct power to ground shunt.

[Richard M.]

Re: melting power wire.

Joe I'm on my phone, when I get back on the computer in a few I'll get back to you with some ideas.... Rich

[Richard M.]

Re: melting power wire.

Just saw your post. I burned another front harness last week. I pulled it all out and reconnected. Also bought a new horn relay. Turned battery on and the front part is ok but it started to heat up around the fuse connector box on the firewall. All other wires are cool. Fortunately juice was going in for just a second so nothing melted. Since this another ground fault it must be an unfused wire. I think wire to ammeter is unfused so I have to check that and then keep looking. I had it running and driving but I was playing with horn relay again and that is when I burned out harness near that relay. . I also put in the drivers side of air con and I may have screwed things up there. Never a dull moment. Any other thoughts would be appreciated. Also taking an online course on electrical wiring in cars

Joe, Sorry to hear your troubles have returned....

Which connector block is heating up, inner or outer? Can you take a few closeup phots of the fuse panel bulkhead block connector/pins?

The Battery Gauge(not Ammeter) is actually a voltmeter pair to display a voltage difference between source and load voltages and is very low current. If there was a power to ground fault there the harness would melt. Unfortunately there are no Fusible Links in the pre 1967 cars so the result you're seeing is from unprotected circuits.

So I don't think it's a power to ground fault. I think what you have is a classic case of a highly resistive and/or misaligned connection in the bulkhead connector for the main power feed for the entire car, excluding the Horn. In other words a bad connection due to corrosive or loose Twin-Lock connector pins. When this high current source connection is loose or corroded, it will act like a low Ohm resistor and heat the wire and those surrounding it in the harness wiring.

I would first check the 12 Gauge Red wire on that inboard bulkhead block, upper inner corner connector as shown in the Frank's Document on page 1 HERE.

EDIT.... Actually I think the Red wire is the Inner Connector, But the Upper OUTER pin. I'm not near a fuse panel bulkhead block to verify though.

This Red wire is sourced from the Horn Relay Buss bar in the engine harness, which is fed from the 10 Gauge Red from the Battery at the Solenoid positive post.

At the bulkhead connections, check to see if the pins in either block are loose or corroded or melted plastic in and around the fuse panel connector block. If the plastic is melted then the Twin-Lock pin in that position will not be in its proper position, and if not it could cause a poor connection to its mating pin in the forward harness bulkhead connector block.

If these mating pins appear loose you may be able to use a small pick tool and VERY carefully reform them by spreading them out for a tighter connection when plugged in. I have done this using a very small right-angle needle nose pliers.

If the pin is badly corroded or loose due to melted plastic you may need to consider a new Dash harness which includes the Panel/Bulkead blocks.

If it's not this, then I have some other areas to check but I'm pretty confident this "Red Wire Syndrome" is your issue.

Edit... One last thing. You might consider adding a temporary 15 Amp fuse at the Solenoid source wire for test purposes until you find the cause of the harness heating up, just to protect your wiring if a hard short happens while diagnosing. Just don't try to Crank the engine as it'll pop that fuse pretty quickly.

Rich

[Michael A.]

Re: melting power wire.

Joe
What do you think of your online course? Would you recommend it?

[Joseph R.]

Re: melting power wire.

It is on an app called Udemy and I ordered Beginner automotive electrical diagnosis and intermediate. I think the 2 courses are 39.00 and I am not sure of value yet. I have gone through 25% of first course. I have learned some stuff and now I understand even though low voltage amps surge through wire if there is no load ( v= ir )

[Michael A.]

[Michael A.]

Re: melting power wire.

Rich
As usual your recommendations are clear and thorough. Thanks for sharing with the group. My only add is related to the fuse suggested for the temporary safety used for testing. 15A is good for protecting the harness but is likely to pop if you test the headlight motor. That’s what happened to me yesterday. I thought about it and then recalled there is a 30 or 40A circuit breaker for the headlight motor which suggests it can draw a lot more current. So I replaced the blown 15A with a 25A fuse. The headlight motors have worked fine with the bigger fuse. Hopefully 25A wouldn’t damage the rest of the harness if there is a fault.

btw - thank you for the restoration archive that has been pinned to the top of the TDB. I just noticed it yesterday and found the Wilcox article for testing the wiper motor which I will be putting to use today. Great stuff!

[Richard M.]

Re: melting power wire.

Mike, Good catch, forgot about the motors. But just to check harness integrity when battery is. first connected without energizing anything, 15 is a good basic startpoint.

Rich

[Joseph R.]

Re: melting power wire.

I actually had a bent pin but I can't remember which connector. I straightened itand I guess I should try again. It has been difficult to get those connectors to set. I do remember that there was one connector that was warm but I don't know which one.Any thoughts on which connector I should try first inner or outer. I have a battery disconnect switch that is one of those circular ones that I can reverse in one second so that I don't damage the harness.Thanks again. I used to have support from my brother mike Romano but he passed away suddenly last year and he was so enamored with his antiques and now I don't have him to talk to. He gave his 63 split and his 28 chevy and his 1908 red to my son so I do have those memories that I can reminisce

[Richard M.]

Re: melting power wire.

My post got deleted using Mobile View trying to edit it.. Its a known bug.

Joe, Inner. Towards center of firewall. One of the top 2 pins is the Red wire.

A picture of panel bulkhead connectors would be helpful. PM me if you want to send via email to me and I can post them.

Rich