Alternator / voltage regular problem

[Dan East]

My 2005 explorer has got a power problem, and it's completely backwards from the typical alternator problems. First off, the battery is good. I had it checked and the cranking amperage is fine. It starts right up like normal.

The problem is that if the RPMs go above around 2800, the voltage drops to the point the computer beeps and warns me. Voltage seems to peak around 1000 RPMs, so it is lower at idle (around 800 RPMs), and goes down as the RPMs go above 1000. I can drive around town all day, as long as I take it easy and keep the RPMs down.

The belt is not slipping - I'm sure of that.

So is this the alternator or voltage regulator? Anything that can be fixed without swapping out the whole alternator / voltage regular unit?

Less than 4 years out of an alternator with only 30k miles on it is pretty crappy. Everything under the hood looks brand new - I don't know if I've even taken the thing on a gravel road before.

 

[jp450]

If I am not mistaken the regulator is an intregral part of the alternator. Remove the alt and take to AutoZone, or similar place and have them test it out on the machine.

It does sound like the regulator is shot...

 

[micachu]

I just got done dealing with battery and alternator problems of my own a few weeks ago. I looked into rebuilding the OE one but I don't have a soldering iron powerful enough to solder on a new diode pack. However the voltage regulator is easily removable once you have the alternator off. I found OE spec and HD regulators here ( http://www.alternatorparts.com/3G_products.htm ) for around $20. I would recommend calling and asking if the new regulator comes with a fresh set of brushes or if the old ones have to be re-used. If the regulator doesn't come with brushes, you can get them from the same site for about $10.