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dftalent

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Discussion starter · #1 ·
I'm looking for ideas on what may have caused a section of my positive wire to melt. We just had the engine running to make some carb and timing adjustments. The next day, my son went to the car to start the engine and adjust the valves. I wasn't there but he told me as soon as he keyed on, this section of wire smoked. I was able to carefully remove the 12 ga wire from the rest of the wires in the harness and don't see any signs of a direct short to ground. This is the original equipment harness. The only modification I made was to run a 10 ga wire from the starter BATT terminal to where the previous owner cut it for some reason.

The front clip is not on the car. The battery is connected to the starter and to the engine block. There are no other grounds connected. I've been involved in automotive fire investigations in my career and I remember that the forensic investigators would say that a positive wire was seeking ground that caused it to melt. Is this a possibility?

Here are some pics. I'm about to repair the harness and would very much like to avoid a repeat of this event.

Thank to any and all input.
Dennis
 

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#3 ·
Unless the wire was chafed and shorted to bare metal, I would disconnect the alternator output and check the stud for a short to ground. Also wondering why a fusible link didn't protect the harness, possibly didn't have one.
 
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#4 ·
That's quite a few places where it's melted - I would start with the furthest point from the alternator/battery where it's melted and look for a short. With the front clip off, could there be a wire with an uninsulated connector that shorted to the frame or body?
 
#5 ·
dftalent said:
The only modification I made was to run a 10 ga wire from the starter BATT terminal to where the previous owner cut it for some reason.
Click to expand...
Can you explain the modification referenced above? Not sure what year vehicle this is, but I'm questioning why tapping 12V of of the BATT terminal on the starter. Maybe that was done on some model years - but not that I'm familiar.
 
#6 ·
What year?

This is the kind of carnage you see when the factory fusible links are removed and replaced with regular wire or they are by-passed for "modifications".....
 
#7 ·
I believe your car is a 64, there are no fusible links on the 64. The carnage cause looks like either a bad voltage regulator and /or alternator.
 
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Discussion starter · #9 ·
RICH1965 said:
You have a short somewhere, are you sure the other stuff is original?
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Thank you for the reply. The harness itself is original as is the alternator. Long story but I owned this car in 1972-1979, sold it to a friend's brother and he had it for the past 30 years. He didnt do much to the car until it was in a garage fire. Other than headliner, w/s, rear glass and paint, no other damage from the fire. I bought the car back and started restomod.

I had to replace some missing parts, voltage regulator and horn relay but other than that, all original. The one thing I see that I did incorrectly was connect the main power supply to the battery terminal on the starter vs running it along the core support to the horn relay. The main 12 ga power wire was cut for unknown reason and he ran it through the gutter on the firewall. I assumed, incorrectly, that this wire picked up battery voltage at the battery terminal on the starter.

Looking at assembly manual, 12ga red runs from battery junction block to the horn relay along the core support.
 
Discussion starter · #10 ·
pnugene said:
Unless the wire was chafed and shorted to bare metal, I would disconnect the alternator output and check the stud for a short to ground. Also wondering why a fusible link didn't protect the harness, possibly didn't have one.
Click to expand...
This is a 1964 Chevelle. From what I've read on the forums, GM didnt use a fusible link in '64. That being said, I reviewed thge wiring from MAD Enterprises and below is how they interpret the wiring from the battery to the horn relay. Lookiing at this diagram, wouldnt the 14 ga fusible link still be picking up 12v from the alternator output wire?
 

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Discussion starter · #13 ·
Coppertop said:
What year?

This is the kind of carnage you see when the factory fusible links are removed and replaced with regular wire or they are by-passed for "modifications".....
Click to expand...
1964. From what I've read on the forums, fusible links were not used in 1964. I may have not grounded the core supportr properly as the front clip is removed. The fender is supposed to have a ground from the battery that would than attach to the core support which is where the voltage regulator is mounted. I will be adding a fusible link. Thank you.
 
Discussion starter · #14 ·
Jim's69Ragtop said:
Can you explain the modification referenced above? Not sure what year vehicle this is, but I'm questioning why tapping 12V of of the BATT terminal on the starter. Maybe that was done on some model years - but not that I'm familiar.
Click to expand...
Thank you for the reply

The car is a 1964. When i purchased the car, the main 12 ga power wire was cut for unknown reason and the previous owner ran it through the gutter on the firewall. I assumed, incorrectly, that this wire picked up battery voltage at the battery terminal on the starter. Looking at assembly manual, 12ga red runs from battery junction block to the horn relay along the core support.
 
#15 ·
Electrically, there are many ways to make the circuit work. Make sure you have an alternator that is made for an external VR. Who knows what previous owners did over the years and may have installed one that is internally regulated and modified the wiring accordingly.

The diagram you posted is for a 69 and up. There are better ways to do it without the splice.
 
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#17 ·
Thank you for posting the year.


dftalent said:
The only modification I made was to run a 10 ga wire from the starter BATT terminal to where the previous owner cut it for some reason.
Click to expand...
We definitely need details on this "tid-bit" of information to rule this out of the equation.

There is no 10 ga. wire on a stock '64 starter.

3 wires. The large main battery cable, the 12 ga. wire connecting to the "S" terminal on the starter solenoid (closest to the block) that delivers 12 volts when you hold the key in the cranking position and the 18 ga. wire that connects to the "R" terminal on the starter solenoid that allows full voltage to the stock points ignition coil (+) when cranking.

Whatever happened, I would agree with the others. There appears to be a direct short to ground from the main 10 ga. red power lead.
 
Discussion starter · #18 ·
Thank you. I know that I wired the 10ga wire incorrectly, at least now I do. I'm hoping to get time this weekend to start troubleshooting and repairing the harness. I also realize that the + battery cable is supposed to have a 12 ga wire going across the core support to the horn relay on the drivers side. I will rectify these issues and let everyone know what I learned.
 
#19 ·
Consider replacing the alternator with the internally regulated type, and getting a kit and rewire the whole car. I just did mine because I was tired of chasing ghosts, kicking the fuse panel to get the lights to work, and finally one direct short. Not as hard of a job as it looks, and now I have peace of mind that the car won't burst into flames at some random moment.
 
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