Q: on. I checked the output of the alternator and the voltage of the battery on (13.90 v) and off (12.67 v) and everything seems to be okay. Any suggestions?
A: 12.67v while off is actually a little low. Your battery, when fully charged, should show around 13-13.2v, and while charging should see about 14-14.5. It sounds like maybe your alternator isn't quite delivering the way it should. Get it checked.