i have a 2000 xj and im having some issues. first off my new year started off great, i hit a dear and new years morning and now im having more problems then just a couple dents. my battery guage lately has been pinned all the way to the max but it doesnt happen all the time. it will happen randomley, all of a sudden my check guages light will come on and when i look down the guage for my battery is all the way up at 19. i have been noticing that my lights have been flickering when i drive but they dont seem to get dim and just today i went to the store my guage went up i parked in the lot went in the store and when i came out my car was completley dead. i had it jumped and it started right up and i drove it home, but the whole way home the gauge was pinned again, when i parked it i shut it off and tried to start it and nothing. so my question is would that be alternator or the battery, granted i didnt test the battery yet because this litteraly happened about fifteen min ago and i dont have a tester. any help or suggestions would be great. thanks

Remove and clean battery cables and battery posts. Until they are shiny.

After that, you gotta test.

Test your charging system first. You would need a meter at the battery (looking for about 14 volts) or have a shop or parts store put their tester on your engine.

Freshening all of your engine grounds is NEVER a bad idea.

Grab a multi-meter and check the voltage while the engine is running. It should be 13-14.5. Any lower or higher then you have an alternator issue.

ditto

agreed

this sorta happened to me. i replaced my terminals. and they were loose where the cable connected and where it connected to the post. also. make sure your battery hold down is on taught . but i would try the free fix first. or look up how to test your alt with a RUBBER handled screw driver.

This exact same thing happend to me three weeks ago. I ended up with a shot battery and a bad alternator. I had to replace both. I think the Alt was the real issue but the batter ywas ruined because having to drive 60 miles with it like this. Go have them tested but be prepared to replace one or both.

the voltage regulator is controled by the pcm had this exact problem when i bought my jeep and i got it extreemly cheap if they use the same charging system ( mine is a 92) ... wiggleg the conection to the pcm and it would go back and forth between max and none at all if it was like mine the pcm was bad

yeah i called up autozone and asked the guy on the phone if he knew anything about alternators and he told me yes, so i told him what was going on and he immediately told me i have a major wiring problem and need to take it to the shop before my car starts on fire. i kind of chuckled and hung up, i dont think he wanted to look up my part. so i called my buddy and he pretty much told me the same thing you guys did about it being the regulater in the alternator and i should just remove the alternator and have them bench test it just to be sure and im pretty certain that my battery is fried. thanks for the help though i really appreciate it.

also one more quick thing. im supposed to take my car out to get an apraisal tomorrow(from that deer i hit) and its about ten miles away. do you think i can drive it there and back without destroying anything other then the battery or alternator because both of those are pretty much done.

No

Replace your PCM, the voltage regulators are very problem prone in cherokees. It takes about 15 min to swap out.

Although either component (voltage regulator or alternator) certainly can fail, from my experience working with the charging system on the XJ, the alternator fails way more frequently than the computer/voltage regulator.

That wouldnt cause overcharge though. if the alternator was overcharging, the bridge rectifier would stop working and you would just get AC going to you battery.

How much does a new pcm run?

You can usually find reconditioned ones on ebay for around 200. Just got to make sure it will compatible with your jeep, and the company is reputable.