weeksj27

Twice over the past week i was driving, and just for a few seconds, the battery light illuminated and the headlights and dash lights got much brighter while the battery guage showed near 18v.

1990 F150 4.9 2WD. Im thinking maybe the regulator but there is a squeal coming from one of the accessories. I think its the alternator.

sylver91

Do you know if your regulator is internal or external?

weeksj27

It is internal. Had the alternator out 2 weeks ago for one of my classes, we tested it, and it tested fine at the time, however it is old.

sylver91

Altho your regulator is most likely done, check for loose alternator and regulator grounding screws. Or if you have a multi meter, with key on run position, put the negative lead on the back of the alternator case and the positive on both regulator terminal screws. If the voltage is different then either a bad regulator, grounded brush or grounded coil.

weeksj27

Im positive everything is tight, i will double check though. But does that sound like a regulator problem?

sylver91

Maybe, just because it looks like one doesn't mean it is. Would suck to replace it, only to have the same problem Thats why testing is important.

weeksj27

Was that test u mentioned with engine running or just key in run

sylver91

Key on run, engine off.