I just replaced my voltage regulator (symptoms: voltages fluctuating wildly from 13.5-15.5 while driving). On re-install, the alternator light wouldn't go out. I pulled it back out, took it to a local DC electrical shop for a quick $5 test before I shipped it out for a rebuild ... and it tested good. He said it generated 14.2V real solid, no problems.
So I put it back in the car (long painful hassle, but I'm getting really good at it now) and started troubleshooting. With the car off, the voltage reads 12.5-13.0ish, depending on what loads I have running. That's gotta be just battery voltage. With the car on, it reads 14.6V. Adding loads (lights, radio, etc.) lowers the voltage slightly, but not significantly -- which would lead me to believe the alternator and VR are both working correctly. Changing RPM does not alter the voltage, which is rock-solid steady now.
But the light is still lit, and I don't know why. My best guess is that I have the wrong wattage bulb, but wouldn't that cause problems with charging? And wouldn't the bulb wattage be associated with the alternator rather than the VR, which is the only new part? So my alt/VR gives every indication of working correctly, but the warning light won't go out.
Help?
TIA,
Dan