Charging issue that is intermitiant

JIM OF TENN

MEMBER
2002 DODGE DAKOTA
160,000 MILES

Voltage reading upon starting often is low and will soon drop to zero and set check gauge light on. When I reset the ingition switch from run to off and back to run position quickly, to prevent the engine from stopping, the voltage reading will eventually come up to mid-range and stay there for the duration of the run time. Re-setting of ingition switch takes anywhere from a couple of times to as many as a dozen or more. All electrical functions seem to work fine both during the low voltage time and after the voltage reading comes up to normal. Have been told the alternator/regulator is bad and that possibly the ignition switch is the cause. Any ideas?

Monday, January 9th, 2012 AT 5:40 AM

1 Reply

CARADIODOC

MECHANIC
34,330 POSTS

Sounds more like a bad diode. Have the alternator load tested with a tester that shows "ripple". If the ripple is high and the maximum output is close to one third of its rated capacity, (30 amps from a 90 amp unit), one phase is dead. That's almost always from a defective diode.

Nippendenso alternators also develop worn brushes that will cause intermittent operation. To identify that you have to measure the two voltages on the two small wires on the back of the alternator while the engine is running and while the problem is occurring. One must have full battery voltage. The other one must have less but not 0 volts. If you find 0 volts on only one wire, the brushes are open. I recently replaced mine for nine bucks.

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Tuesday, January 10th, 2012 AT 12:22 AM