1996 XJ Sport 4.0L 4X4 5 speed with 150K

Driving home yesterday, my radio starting turning off intermitently. Discovered it would happen when the AC clutch engaged (the voltage would drop down to just above the red mark but come back up to middle). Turned off lights, AC, fan, and radio and the voltage gauge went high almost to the red mark. Turned fan on high and gauge went back to about 14 (where it is supposed to be). But when came to stop light and engine dropped down to idle RPM, voltage dropped down about half way between 14 and the top of the lower red mark. At some point the GEN light came on. Basically, it looks like the voltage output from the alt was not being regulated properly. This continued until I got home (about 30 min drive). I had asked in the "ask a question" forum if the voltage reg was part of the alternator or if it was separate and was told the reg is in the PCM (I'm assuming the PCM is the computer). Started it this evening to go to work and everything is working normally. I thought that maybe a quick alternator change might take care of it, but if the regulator is part of the PCM, it might not be as straight forward as I thought.

 

I think the voltage regulator is built into the alternator but i would try the alternator first anyways, I would imagine its alot cheper then a PCM just my opinion good luck on getting it fixed

 

after 90 regulator built into ecm hit auto zone have them test chargin situation