Is my altenator going bad? Is it the voltage regulator in the altenator that is failing?

CAR = 94 GSR with 115,000 miles

PROBLEM IN THE BEGINING = cranks but does not turn over the first try. It will turn over the second time. This is an intermitent problem.

PROBLEM NOW = while driving and at idle, the tach needle drops below 500 rpm and then

jumps up over 550 rpm, In addition, the headlights are dim the brighten up when reving the car at idle.

Recently at a stop light the car sputtered and died. It restarted after the first turn of the key. Then it sputtered and died a 2nd time at another stop light and restarted after the first turn of the key.
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- I tested the battery with a voltmeter and I get 12.78 volts with the car off. I tested the altenator by connecting the voltmeter to the battery and with the car idling I get 14.63 volts.
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- Altenator, starter, fuel pump, fuel pressure regulator have never been replaced.

- The battery is 2 years old.

- I have replaced: coil, ignitor, main relay = these parts failed awhile ago

- Distributor cap and rotor, sparkplugs, ignition wires have been replaced as routine maintenance.

- Fuel filter = just changed it.

- Fuel Pump = has not been replaced but I hear it prime when I turn the key to the 1st position.

 

ever done a tune up on your car?

 

I thought the voltage regulator on an altenator goes bad if it reads over 14.5v. I tested the altenator by connecting the voltmeter to the battery and with the car idling I get 14.63 volts.

 

14.5 v being normal is sort of a simplification. Depends on temperature & a couple other things.

The difference between 14.5 & 14.63 can be explained by inaccurate voltmeter. Got a $250 Fluke with up-to-date calibration?

 

http://www.2carpros.com/how_to/battery.htm

Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.

 

Possibly the alternator, sounds more like you have bad connections though. Check your ground's as well.

Something to think about: Most auto parts store's will check the Charging and Starting system free of charge.

 

I had it checked at autozone and kragen but their tester only reads pass or no pass, no voltage reading. I took it to an altenator shop and they said it is 15v but they would have to open it up to check it so the tests didn't add up to much.

 

Starting problem is resolved. I took out the altenator and had it completely rebuilt at a reputable altenator shop. Altenator shop said the altenator was still good at 15 volts. But before rebuilding the altenator it was had to start the car; now I don't have a starting problem with the rebuilt altenator.

I tested the rebuilt altenator by connecting the voltmeter to the battery and with the car idling I get 14.4 volts.
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Idle problem: At idle, the tach needle drops below 500 rpm and then jumps up over 550 rpm, In addition, the headlights are dim then brighten up when reving the car at idle.

Idle problem solved by unbolting and cleaning IACV with carb cleaner.