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ramman05 12-23-2010 07:05 PM

1985 c3500
 
I have a 1985 c3500 w/350 motor. Alternator output has been low lately and battery was only charged to about 300 amps. The voltmeter would read 13 volts
unless wipers and headlights were on at idle then it would drop to about 10v. I decided to replace alt. and the 1st one immediately read 8v. at idle under load. I was given replacement and same volt reading approx. But it checked out with load tester. Left and drove around town on errands. Headed home on highway and noticed voltmeter was completely off. Returned to parts house. Checked wiring diagram and could find no fuse for gauge. Checked wire to gauge with 12v test light and I had voltage. The parts house checked alt. and it was fine with about 14v output. Is it possible that when I hit high rpm on freeway that the alt. sent to much voltage to gauge?

auto123 12-31-2010 02:43 AM


Originally Posted by ramman05 (Post 62224)
I have a 1985 c3500 w/350 motor. Alternator output has been low lately and battery was only charged to about 300 amps. The voltmeter would read 13 volts
unless wipers and headlights were on at idle then it would drop to about 10v. I decided to replace alt. and the 1st one immediately read 8v. at idle under load. I was given replacement and same volt reading approx. But it checked out with load tester. Left and drove around town on errands. Headed home on highway and noticed voltmeter was completely off. Returned to parts house. Checked wiring diagram and could find no fuse for gauge. Checked wire to gauge with 12v test light and I had voltage. The parts house checked alt. and it was fine with about 14v output. Is it possible that when I hit high rpm on freeway that the alt. sent to much voltage to gauge?

It is possible as there is temperature gauge present in the vehicle.. when you increase the RPM, the voltage can be increased and transferred to the gauge...


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