cnelson14

I have an 89 Audi 100 that has recently been giving me some troubles.

I was driving around town a week ago and the voltmeter dropped rapidly(from around 14 to 8) within 2 miles. Pulled into a parking lot, kept engine on and within 30 seconds the engine shut itself off. Tried to start the car up and I got a burst of clicking when turning the key. Called up AAA and had a tow truck jump me. Car starts but voltmeter is low and within 1 minute the engine dies again. Tow truck takes me home.

Removed the battery and went to Kragen(local autoshop). They put the battery in a charger and juiced it up for 15 minutes. Take battery home, place it in car, and it starts up fine. Drive back to Kragen and they test the voltage at the battery (located under the backseat) and gives a normal reading (sorry not sure what that reading was). Then they test at the alternator and it gives a reading of 13.6V.

The battery itself was over 80 months old so I decide to replace it. Get a new battery place it in, and everything works fine for one week of light sporadic driving.

Today the car starts normally except for the voltmeter staying around 11V. Additionally the "alternator warning light" on my dashboard along with "brake warning light" and "anti lock off" warning light come on. All three stay dim.

Checking the owners manual it says the alternator warning light comes on when, "there may be a malfunction in the electrical system or the V-belt driving the alternator may be loose or broken."

Regarding the brake warning light; "if the light remains on after the engine is started and the parking brake is fully released...it may be due to,
1.Brake fluid level is too low (Its fine)
2. Insufficient hydraulic fluid in the reservoir (Its fine)
3. Pressure for the hydraulic brake booster is too low (no idea on how to check)


After having read and searched the forums I found "https://forums.audiworld.com/v8/msgs/96845.phtml"

His problem seems similar and so I am wondering if I need a new alternator, a new voltage regulator, or both? Or are there any other suggestions you may have?

Thanks,
Cee Nelson

mcorrow

Sounds like the brushes are worn down. It's fairly easy to get to, you can actually remove it without undoing the alternator... there may be a plastic cover on the back that you need to remove (4 8mm nuts), then there are 2 screws holding the VR in place. If the brushes are nothing more than "nubs", that is most probably your problem.
you can also test the alternator with a voltmeter -
postitive is the large terminal, to any ground (while the car is running), should get 14.0-14.5 volts (depending upon which VR you have)...

Good luck!

fkess

Since replacing the battery last year in my '91 100, the gauge does not read as high as it used to but I've had no electrical problems ...yet.
It reads about 12-12,6. It used to read about 13. I stopped thinking about it.
Floyd

cnelson14

Thank you mcorrow,
You were correct, the brushes were worn down. Bought a new voltage regulator, followed your instructions and problem solved.