Surging and dipping voltage.

When driving my '92, my voltage guage alternates between around 10 to around 13.

I had the case of the alternator apart a few months back to clean out mud. While I had it apart, I noticed the brushes were well worn.

I understand the regulator is built into the computer.

What do you think the problem is?

TIA

Okie Terry said:

When driving my '92, my voltage guage alternates between around 10 to around 13.

I had the case of the alternator apart a few months back to clean out mud. While I had it apart, I noticed the brushes were well worn.

I understand the regulator is built into the computer.

What do you think the problem is?

TIA

Click to expand...

Bad ( dirty ) connections, bad alternator. One of the 2.
If the brushes were worn, I'd start with replaceing the alt.

One possible problem is the voltmeter itself. You can't really trust the reading because it suffers from voltage drop, and the gauge itself is not all that good. Try measuring the voltage at the battery itself and see how it agrees with the gauge.

As far as the brushes are concerned, there should be a good tolerance for wear, but if they lose contact, there will be no charge at all. If they're intermittently losing contact, you might well see a variation between 10 and 13, but you might need a second, trusted voltmeter hooked to a different circuit to catch it red-handed. If the alternator was full of mud, it's possible the slip rings got dirty, and since the brushes have a very light spring they won't cut through the junk. It might be worthwhile to find some non-sparking contact cleaner and see if you can shoot some in there. If you decide to open up the alternator again, don't sand the slip rings, though. They need to be very smooth. Crocus cloth works well.

One relatively simple test is, when the voltage is reading low (and if it's low at the battery too), is to give the alternator a whack with a long stick or something. If vibration raises the voltage, it's a pretty sure sign your brushes are worn out.

Okie Terry said:

When driving my '92, my voltage guage alternates between around 10 to around 13.

I had the case of the alternator apart a few months back to clean out mud. While I had it apart, I noticed the brushes were well worn.

I understand the regulator is built into the computer.

What do you think the problem is?

TIA

Click to expand...

You've answered your own question. Replace the brushes.