Instrument cluster warning lights on and go off only at 3000 or above RPM. 700 1988

I would suspect the alternator circuitry. Sounds like you need a new brush/regulator set.

I ran the car and used a voltmeter to see the voltage across the battery with car on and off. It is around 8-9Volts off and shy of 12Volts when I revv it to 3000 RPM or so.

So, I guess the Voltage regulator and the brushes are the easy thing to do for now. All connectors seems to be good enough. I have isolated the battery terminals and no build up or corrosion is noticeable there.

I hope that the alternator is not becoming bad itself. How do I test for that? fcpgroton has the regulator for $24 and the rebuilt alternator for $150. So, I hope I can get away with just the regulator.

I will take your advice and take the battery to advance auto parts to test it. I got this battery from Costco in 2004 so it stayed for almost 4 years now so I won't be very sad about it.

I drove on it like that for around 15-30 minutes.

I have a question though about the alternator, that I hope someone can answer for me, how do I know if the alternator is good or not after the regulator and brushes are replaced?

If you're only measuring 8-9V across the battery when the car is NOT running, that sounds like you have a bad battery at the very least! Maybe a shorted cell in it...

I think I'd pull the battery, check the voltage across it, and if still low, I'd try putting in a new battery and see how things look...

That's not to say you don't need to replace the regulator or the entire alternator, just that you should start with the battery and see. Batteries don't last forever, and even a new one can fail....

Hameed,

That's simple, it will either work, generating approximately 13.8 volts at fast idle speed with all the electrical equipment that the car has switched on, or it won't work, outputting an inadequate low voltage. As an aside, I have known a regulator/brush packs to be perfectly OK, the alternator to be perfectly OK, but, the output voltage to still be low. Causing the car to eventually break down. The problem? Well it was simply a dirty contact between the regulator and the alternator (not the brushes), once it was cleaned up the alternator worked beautifully.

Best wishes, Ken Phillips

I have changed the regulator. The brushes were worn out. It was not a hard job to do when I changed the regulator and brushes.

The battery was fully charged when I tested it in Advance Auto Parts and they left it for 20-30 minutes until it was fully charged.

Now, the battery reads 12.5 volts without connection. It measures after the car is started and the lights are on 11.99Volts.

I guess I am not seeing the 13.5volts because the battery is already charged, right?

Hameed,

Apologies for sounding pedantic, but, I'm not clear what you mean when you say "after the car is started". Is the engine actually still running while you are measuring the battery voltage? Is the ignition warning light extinguished when the engine is running? If so, then even with a depleted, but, otherwise good battery, the terminal voltage of the battery should still be in the 13.5-13.8 volt range (sometimes a little bit higher), even if everything electrical is turned on. Sometimes the engine needs to briefly run at about 1000 rpm to properly energise the alternator. If the above isn't seen, then check the earth wire to the alternator body from the engine block, the B+ wire (thick red one) to the battery via the starter solenoid, and if possible the integrity of the ignition lamp wire, following it (the thin wire) from the alternator to the grey multi pin plug at the side of car. Look for breaks, inappropriate grounds/shorts, worn/missing insulation, and frayed connection terminals.

TTFN Ken

No problems at all.

I drove the car after I changed the regulator and I measured across the battery and it is 14 Volts. With no the car off, the volt was 12.

So, I guess everything is in order now.