my alternator light seems to have a mind of its own. it is on about 30% of the time. sometimes for the whole drive, some times not at all. tonight it turned on while cruising down the freeway but turned off about 2 minutes later. when the light is on everything runs as normal, the headlights do not dim as would be expected, and i've never had a problem with a low battery charge, so i think maybe the light is possessed? what triggers the signal for the dash light, and how do i go about making sure its operating correctly? i'd rather not buy a new alternator when the one i have seems to work just fine, aside from the dummy light always coming on.

Al

 

check the voltage coming out of the alternator while the light is on, seems like the brushes are sticking. you can smack it with a hammer and get the hung brush to pop free, or just buy a new brush set from the dealership, (around 20 bucks) and rebuild your alternator. also could be the belt slipping on the pulley.