01 Jetta Battery Light

Here's one I THINK I know the answer to, but thought I'd throw it out here to see if everyone agrees.

My TDI Jetta just started to throw a battery caution light on the dash last night. I investigated a little driving it home, because it was intermittent, and found it only came on at 2550 +/- 50 RPM. If I slow down, it goes out. If I speed up, it goes out. It doesn't ALWAYS come on at 2550 RPM, but it never comes on at any OTHER RPM. The light is accompanied by a minimal decrease in headlight strength, and when the light goes out the headlights come back up to full strength.

My guess is the voltage regulator starting to go, and I'm also guessing the regulator is in the alternator. Haven't seen one OUTSIDE the alternator in years, but who knows, I haven't checked out the Jetta yet.

How does this sound to you folks? Reasonable assumption I have an alternator ready to be changed?

Sounds about right.

And the regulator/brush assembly is indeed inside the alternator. It is replaceble.

You might also check wiring that may be vibrating loose.

They say on the later models it is not replaceable. Don't know which years though.

They became non-replaceable with the '01 model year.