Alternater whackin'

The alternator in my '91 4.0 has been giving me some trouble lately. Whenever I start the Jeep, and sometimes going down the road, the volt gague drops to 10-12 volts. While wheeling last weekend it got lower than that and the vehicle died. But, if I get out and use a bar and a hammer to smack it, it starts charging again. I have also had it jump back up after I hit bumps on the road. Has anyone else had this problem. I'm thinking voltage regulator. These are internally regulated, right? Is there something else I'm overlooking. I don't want to drop the $$ to replace it before I persue other options.

check the connections at the alternator maybe they are loose or corroded, if not maybe brushes inside the alt.

The wire connection is sound, sorry I didn't put that in my first post. If I pull this to check the brushes, I will just replace it and throw this one on the shelf for a spare. I feel that is where I'm headed, I just want to make sure that there is nothing else that I am overlooking.

mine got so bad, i was whackin' it with a maglite everytime i cranked up....... so i bought a used one on ebay for 6 bucks......charges like champ!! gonna get the old one rebuilt at a local alternator shop, maybe they can bump up the amperage!! good luck,

Same principle that makes a bad starter give a few more starts with a solid wack. Brushes are worn. Time for a rebuild/replacement.