INTERNAL voltage REGULATOR

I have been doing some searching and have not got under the jeep yet but dont the 89 alternators have internal v/r's? thanks

I think you are correct but I'm not positive, give me a little while and I can tell you for 100% sure. My fiancee should be home any minute and since she rebuilds alternators for a living and drives an '89 XJ she'll know for sure.
Tony

She's here. Yes your '89 is internally regulated. Also says that the regulator is probably not bad, but the rectifier is most likely the source of any problems, unless it is overcharging which would be your regulator.

thanks for the quick response, I got mud in the alt. and it only works once in a while? guess I'll have to fork out the big bucks to get this alt. Atleast it takes care of if it is the alt or the reg. thanks

Mud may have jammed up the brushes in that case. It might be worth your while to check it out.

Probably mud under the brushes, I use very hot water sprayed onto the brushes (in the rear) while rotating the shaft by hand (really have to remove the alternator). Spray it out with very hot water, then blow it out with air. I´ve done it often, with no real bad affects on the alternator.
To get the insides of the alternator really clean you have to spit the case. It´s easy to snap off the three bolts holding the case together. Mark the case before spitting (so reassembly isn´t guess work). Keep the front cover and the shaft/rotor, in one chunk (like fig. 6) and the rear cover and the stator (fig.7) in one chunk. The rear cover and the stator are connected by wires (got to de-solder to seperate, which is rarley necessary.
I´ve seperated my alternator, many times (first time is hard, after greasing the case bolts it´s easy, the next time). May have to buy a special socket for the case bolts, depending on how complete your set is. Easy to snap off the case bolts, penetrating oil, tapping the bolt with a hammer and heat may help (not too hot).
May want to try cleaning it out by spraying really hot water into the rear air vents, without splitting the case. Better to make sure everything is thoroughly dry, before firing it back up. There is often an amazing amount of mud in the alternator.

If you got mud in it, it's well worth your while to try cleaning it out first. You might even be able to get some results by squirting in some electrical contact cleaner to see if cleaning the sliprings can re-establish brush contact . Make sure it's a non-flashing cleaner. Alternator brushes shouldn't spark, but still, best play it safe.