My car is--- 1999 Audi A4 Quattro. 2.8 liter V6.

Couple of days ago, my BatteryIdiotLight came on and my voltage gauge started to read lower and lower voltage. Then it "fixed itself" (voltage came back).

Yesterday it happened again as I was driving home and the voltage gauge went very low but I made it home. I put my battery charger to work and it recharged the battery. The next morning upon starting the car-- and--- it had fixed itself again!

I believe the problem is a bad regulator. My question--- where is my voltage regulator? It is inside the regulator or external? If inside the alternator how hard is it to replace? If external, where is it?

Thank you VERY much!

Regards--- Rick