I have an older chevy Truck. It is discharging at idle close to 8 and comes up to maybe 12 or 13 on a high rev. How do I know if it is just missing one of those little ground wires ( I had this happen on a Chevy in the past) or an alternator problem? this truck is an 86 and a 350 v8 with a carb and not fuel injection.. thanks for you help guys. I appreciate it.
Take volt meter and test the alternator at an idle, and at an higher rpm on the back of the alternator where the hot cable connects, then test at the battery.. there should only a very little difference between the 2 test areas.. if it reads the same as your gauge you an alternator issue.
If it reads at 12-13 volts at an idle I would suspect a ground issue, remove and clean ALL grounds and retest.
BUT….It sounds to me you have either a bad set of brushes or a diode out in the alternator.
Feel free to call me with any questions.
Jeff 507-696-6722
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