Battery light when cold.

[techspy]

Hi All,
Recently I have been having my battery light stay on 10-30 seconds after starting up. It only happens when the engine is cold. Usually after sitting over night or for several hours is when this happens. I can rev the engine and the light will get dimmer. It doesn't come back on throughout the rest of the day and seemed to start this once the weather has gotten cooler.

Any ideas?

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

[techspy]

Thanks fo the info Jim. I should have added that I have a new battery (sealed Optima type). I checked the voltage engine off and got right at 12v. I started the engine and for about 10 sec the battery light was on and the voltage dropped to just about 11.5 volts. When the battery light went off the voltage went up to just about 13.5 volts. So its obvious that the alternator isn't charging for those first few seconds after starting up.

So do you think the alternator needs rebuilding or could it be that the regulator needs replacement? I have taken the alternator off an 83 Turbo before and I am not looking forward to that challenge again. I will check all the connetions just to be sure that isn't the cause.

John
94 S4

[techspy]

From what I remember one of the bolts was really hard to get out. I believe I had to remove something else that was in the way to get it off.
I am hoping that it just needs the regulator. I will take it to an auto electric shop to check out completly though. It really has me puzzled that it seems to be heat related. Meaning that when it warms up, it works fine. It only happens after a cold startup (for now).
I would like to get the part number for the regulator and have it in hand so I can just pull the alternator, replace the regulator and reinstall.
Does anyone know what parts, other than the regulator, could be going bad? How about a part number for the regulator? I will double check the connections to make sure everything is secure. There should only be 2 wires right? One main one for charging and one for the gauge/idiot light right? It grounds through the bracket right?

Thanks

John
94 S4

[techspy]

Well, I ordered a new regulator from JAE. It's only $25, and I may be able to replace it without pulling the alternator. I will report back with the results.

John
94 S4

[techspy]

Well, I replaced the regulator and it made no difference. So I took it to a local alternator repair shop and they had it back in 2 hours with a new rectifier, new brushes and brush holder, and new bushings and gave me a lifetime warranty. They didn't have the rectifier on hand so he rebuilt the original. All for $80! Working like a champ now.

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

[techspy]

Yeah that black housing is the rectifier and he did ask if the alternator was getting hot quickly, like after 5 minutes. So that was the prob. I did tempt fate with mine as I drove it for a good 2 weeks with the problem hoping it wouldn't leave me on the side of the road.

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

[techspy]

Just an update for anyone else with alternator issues. Mine went out again (12 years since the rebuild) and this time I went with the 14812 from OReillys. It was $90 after the core return. I rotated the basket to get the wire connections closer to the OEM. The bolts were phillips head screws and very hard to get off. One stripped so I had to slot it. Then when putting them back on, one broke. Hopefully 3 is enough!