Alternator Wiring burnt up. I need so help

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Alternator Wiring burnt up. I need so help

Postby Collers9640 » Mon Feb 12, 2018 5:36 pm

I was coming back from lunch today and all the sudden The ammeter started to peg then about a minute passed and smoke filled my gauges, so I pulled over and turned off the truck.
Before I start my with what happened does anyone know what would cause amps from the alternator to jump up and stay high enough to burn up the wire harness?
(My truck is a 77’ Power Wagon cummins Conversion)
I popped the hood and checked the alternator wiring. The black charging wire that runs through the bulkhead connector to the ammeter was burnt up as well as the green wire that runs to the voltage regulator. However the red wire that runs that also runs to the voltage regulator Looked fine.
I continued looking around and the the red wire that comes from the ammeter and connects to the starter relay was burnt up very very badly and oddly the fusible link didn’t blow. Next I pulled the cluster and saw that the black wire that comes from the alternator to the ammeter was burnt and the red wire that goes from the ammeter to the starter relay had shorted to the black (that explains the smoke) but what cause it the heat up in the first place?.
What would cause the amperage to shoot up and stay there?
77’ W200 Cummins- Auto, BHAF, 4” Exhaust
91.5 W250 Cummins Conversion- PS I/C, pump maxed, Red Oak Diesel Injectors, Coolertubz, pump advanced 1/8", 3" elbow, 3200 Spring, Piston Lift Pump, KDP fixed, DennyT pin, HX35, 4in Downpipe, BHAF, Heater Grid Delete, Alcan springs, Bilstein Shocks
1984 D350 Crew Cab (Future Cummins Project)
fuel screw!!!!
Posts: 148
Joined: Wed Feb 24, 2010 4:25 pm
Location: Charleston SC

Re: Alternator Wiring burnt up. I need so help

Postby BC847 » Mon Feb 12, 2018 8:48 pm

What you describe is a dead-short to ground.

Look for evidence of a hot (12vdc) conductor shorting to the metal of the truck. Trace all the burn't wires to where the burn stops. Then look hard there. Most likely downstream of the ammeter.

1993 12mm VE Fueled W250 CC, Green
12.67 @ 103.35
Your basic farm truck ;)
Posts: 1957
Joined: Wed Jan 03, 2007 5:22 pm

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