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Melted Alternator Wire

I’ve got a '72 Plymouth Valiant. I just replaced the alternator and voltage regulator after the alternator started making that death noise and smell. The new alternator configuration slightly different, but as best I can tell I’ve wired it correctly.

That said, now when I start the car it runs smoothly, but in less than a minute the wire from the alternator to the voltage regulator heats up to the point that it is melting. I’ve since replaced the melted wire, but I’m hesitant to just start the car because I don’t know what caused the problem in the first place.

Did I wire this wrong? Could another part be damaged and causing this?

What size is the alternator? What size is the wire to the battery in wire gauge size (14ga to 8ga)? A wire will heat up if the wire size is too small to safely carry the amperage load. Here’s a handy guide:

If the gauge size is appropriate, then something is causing a major drain. A short in the battery can do this. I’ve personally seen a battery with enough juice to start a car, but still pull enough current from an alternator to fry it in a heartbeat.

“The new alternator configuration slightly different, but as best I can tell I’ve wired it correctly.”

What is different with the replacement alternator? There should be two field wires and one positive battery cable.

I would guess there is a short in the system. To draw enough amps to melt a wire my first thought is the positive lead to the starter solenoid, the solenoid, the lead to the starter motor, or the starter motor and/or connection. Ground faults can do weird things also, so clean and check those also.

What is the different configuration? There are three wires on the alternator; the BAT that connects to the battery, and 2 sires marked stator and field as I recall. The field is powered up when the key is turned on and the regulator controls the output by varying the ground. If everything is wired correctly the only thing that would cause the wire from the alternator to the regulator to burn is a failed regulator… Unless the burn occurs in the wire before reaching the regulator.