high voltage - 2000 rodeo 2.2L

[evinity]

I have a 2000 Rodeo 2.2L with 55K miles and have never had any real problems until now.
I was driving the other night when the "battery" light came on. The "brake" light flickered briefly but then went off. I immediately noticed that the headlights and dash lights got brighter and varied with higher revs. The bat light would get very bright with high revs.
So, I thought this must be a voltage regulator problem. The alternator is obviously putting out current, just too much. I pulled the alternator (Delphi 100A) and replaced the regulator module. Not too difficult. I was really feeling very clever at this point.
But, got it all back together and reinstalled and... same problem... bat light on and high voltage with higher rpm's.
I thought I understood all about alternator and VR theory, etc but I guess there is more than meets the eye here.
Anybody have any ideas? Should I just bite the bullet and replace the alternator?
Thanks

[Canucklehead]

Originally Posted by evinity

I have a 2000 Rodeo 2.2L with 55K miles and have never had any real problems until now.
I was driving the other night when the "battery" light came on. The "brake" light flickered briefly but then went off. I immediately noticed that the headlights and dash lights got brighter and varied with higher revs. The bat light would get very bright with high revs.
So, I thought this must be a voltage regulator problem. The alternator is obviously putting out current, just too much. I pulled the alternator (Delphi 100A) and replaced the regulator module. Not too difficult. I was really feeling very clever at this point.
But, got it all back together and reinstalled and... same problem... bat light on and high voltage with higher rpm's.
I thought I understood all about alternator and VR theory, etc but I guess there is more than meets the eye here.
Anybody have any ideas? Should I just bite the bullet and replace the alternator?
Thanks

There could be an excessive voltage drop in the battery voltage sensing wire to the alternator. This will make the alternator think that battery voltage is less than it actually is causing it to "over-charge" the battery.

[evinity]

Interesting. Where would the sense wire be connected to the alternator? There are only 2 wires (plus the case ground) going to the alternator: 12V input for the field and the high current ouput terminal. The voltage regulator is internal and connects directly to the slip rings, etc. It seems like it must just sense the output voltage. Voltage measured at the battery terminals is the same as I am reading at the cigarette lighter - 14.7 to 16V. It would probably be higher if I did higher rev's but I don't want to burn everything out by letting it go higher.