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16 volts instead of 12 a problem?

I have a 1994 Chevy Corsica with a 6 cylinder engine. In recent days a red light that is shaped like a battery on the instrument panel has began coming off and on intermittently. It comes on for a few seconds to a couple minutes, then stays off for a while. When it comes on, my headlights get very bright and my heater blower goes very fast. The battery is good. I took a voltmeter and measured the voltage at the cigarette lighter socket. When the battery-shaped indicator light is off and everything's normal it reads

14 volts. When the red battery-shaped light is on it reads 16 volts. The car runs fine either way. This happens during both hot and cold operating temperatures, light and full electrical load, and there doesn't seem to be a pattern. I also hear a faint whining noise coming from somewhere when the light is on. I thought the alternator was dirty so I sprayed it with a garden hose and Joy dish soap, but that didn't change anything. I thought about the voltage regulator, but can't find it. Does anyone know what is going on here and if it's okay to continue driving the car? Thank you.
Reply to
j
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It *is* the voltage regulator. No other component is responsible for voltage regulation.

Reply to
AZ Nomad

Well....... Not entirely true. It can also be something like an alternator rotor with an internal short to ground. On many alternators, the regulator works by varying the effective resistance that is in series with the ground return from the rotor, with battery voltage always being available to the other terminal of the rotor. If a short to ground develops in the rotor, the alternator will charge without regulation.

Reply to
Steve

I wouldn't drive it far that way. Overvoltage can damage various parts of the system.

Something is definitely wrong. It could be the voltage regulator, which is internal to GM alternators I am familiar with. I would check visually for any obvious wiring problems, then take the alternator in for testing...or, just take the car to a competent mechanic and let him fix it for you.

Reply to
<HLS

I know that on many alternators you can intentionally bypass the voltage regulator in order to get DC voltages and currents high enough to power AC/DC tools. In case such an connection were made accidentally, then the result would be higher voltage, regardless of the regulator. If it can be done intentionally, then it can happen incidentally.

But I agree with AZ, it is most likely the regulator.

Reply to
<HLS

Alternators hate joy dish soap. Try dove.

Reply to
Steve Austin

The voltage regulator on this car is built into the alternator. It has failed. It will very soon destroy the battery and may well destroy thousands of dollars worth of various electronics as well. Get it fixed immediately before it destroys the car.

--scott

Reply to
Scott Dorsey

Fix it right away. I used to have a car with a voltmeter display. One Wednesday I saw an overvoltage condition (usually failure of the voltage regulator). I figured to wait till the weekend, when I would have time to replace the regulator. Friday evening the battery was fried. Had to replace BOTH regulator and battery.

The overcharging heats the battery and drives off electrolyte. As the electrolyte gets lower, the internal impedence of the battery goes up, generating more heat, with boils it off even faster. This is a positive feedback runaway condition. It can happen fast, especially in warm weather.

Reply to
Don Stauffer in Minnesota

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