In need of help..Once again..Electrical

92 XJ with 175K 2 year old battery has been starting up fine and running ok. Past 2 weeks amp meter has been acting weird by not moving for about 4 to 5 minutes then jumps up to 12 volts. Today DW takes a short trip and XJ is doing about 35 mph and all guages are bottomed, not working. She pulls over and turns motor off and it will not crank over. Tries to start it and it won't crank. Leaves it for 30 minutes comes back and it starts fine and runs it home. I think its the alt and take it Kragens have it tested and it test fine . Test battery and it fine.
We need help.......Any ideas of where to start with this prob?????????/
Thanks

Had similar situation with my 94. Took it to Checker, all checked fine, pulled the alternator, took it to Checker for bench test, checked out fine. Reinstalled, checking everything, grounds, cables etc etc. Pulled alternator and took it to a real alternator shop, alternator bad.

Replaced alternator 3 or 4 months ago, no further problems.

Just my experience. atriot:

Worn alternator brushes will sometimes do that as they intermittently contact the slip rings. The current through them is very small, and the spring pressure very light. If they've been jiggled enough to make contact, a cursory test won't find any problem.

Thanks...in my limited electrical experience, I thought for sure it was the alt and really wanted a dead alt after the test. Just hate these electrical issues....
Will p/u new alt tomorrow

Thanks again..........