My lights get brighter on my A3......

[booger]

I think your right

 

[Hooper]

Ummm....correct me if I'm wrong but doesn't the compressor belt just run down to the crank pulley and the alternator belt run around the crank and water pump pulley? I would put a digital volt meter on the alternator output and see what the voltage is when the dash needle pegs. It sounds like you're losing your ground for your alternator and its basically full fielding the alternator and will eventually fail.

That makes sense, I will look it over for a lose ground.

 

[G-Force]

Hooper,
Another thing it could be is high resistance or bad connecton on the field wire coming from the power switch.If I'm not mistaken this wire turns on the alternator or tells it to charge when it is energized. If it has a low voltage than 24 volts the alternator tries to boost the voltage up and thus causing the problem you describe. I'd put a volt meter on this wire when it does it to see what the voltage is. If its lower than battery voltage I'd suspect the power switch. Just a thought.

 

[booger]

My voltage meter started pegging whether the headlights were on or not so I decided to hook up a volt meter to the batteries and see what was really going on. I found a loose battery terminal when I was hooking up the leads. I've driven it several times and the voltage has stayed right on 28V and the gauge hasn't pegged once....now that all of the terminals are clean and tight

 

[Hooper]

Need an alernator for my A3.....

So my truck is over charging at times. It is totally random but when it happens the voltage pegs and everything electrical goes nuts. It looks like the regulator is in the alternator. If anyone has one or a link I would be grateful.

 

[doghead]

regulators are available new from Erik's mil surplus.

You may have a bad connection or cable. I would measure each cable for resistance before replacing the regulator.

 

[Hooper]

regulators are available new from Erik's mil surplus.

You may have a bad connection or cable. I would measure each cable for resistance before replacing the regulator.

Thank you, now i know why half of my dash lights don't work.

 

[Hooper]

For some reason when my air compresor runs my voltage surges and all my light get brighter. It will go away as soon as the compressor shuts off. Any ideas?

Update. After buying two regulators I have fixed the problem. The first one I bought on ebay and was called the most common regulator used for the A3. I should have known better....After a phone call to Southern Michigan Automotive here in Michigan, I was able to tell the guy what the wrong one looked like and he knew the correct one. While installing the new regulator I found a couple of fried wires down inside the alternator. Fixed those, installed new regulator and she works perfect!

 

[Hooper]

regulators are available new from Erik's mil surplus.

You may have a bad connection or cable. I would measure each cable for resistance before replacing the regulator.

As an update to this thread, it turned out to be a bad voltage regulator. I ended up with an extra reg in the process but was happy to have found the problem. When I opened up the alt it was pretty toasted in there. Along with the new regulator, they sent me a new one wire capacitor which I really needed as mine was melted. Thanks again.