Jeep charging troubles

1996 jeep cherokee with the mighty straight 6. Customer said its not charging. Bring it in and confirmed. New alternator check my work looks great ship it out the door. A month later he is back. Now it charges 18 volts. Customer seems concerned.

From the studying jeep decided to hide the regulator in the computer.

I've looked the wiring all over very well. Took the battery temp sensor out of the battery box and warmed it up. Scan tool showed it reacted to temp change. Set the temp sensor off to the side. Still charging 18 volts. Battery tests good both with multi meter and a pile tester. Alternator is a month old.

I'm thinking of condemning the computer. What kind of mess am I looking at there. Oh and where do I find a computer for a nearly 30 year old vehicle. I'm guessing my local napa or orielly won't have one handy.

I'm guessing I'll have to program the computer too... I'm a bit over my wheel house here but I hate to say no and he's a good customer.

Probably not your problem, but  2 months ago i put a new battery in a 2019 FLEX.. It has a Negative battery clamp and 3 extra small wires like 16 gauge connected to little studs on the BIG CLAMP... I had to take the wires off to get extra movement of the clamp to get the battery out.. TIGHT AREA.... Apparently when i put the 3 little wires back on i forgot to tighten one little nut holding it to the stud... Week later had all kinds of funny electrical problems. Checked charging and i had 15.8 volts  ... ...... Finally found it when i went to pull the battery back out.....

Edited by steve(ill) - 02 Feb 2024 at 9:59pm

I'm very hesitant to do the computer. I can't see anything else that's bad though. I wish there was a way I could rule the computer bad for sure.

Possible the new alternator is bad? Could it have grounded it self some how? Any way to tell that?

Is the alternator putting out 18 volts, or is the gauge showing 18 volts? Possible faulty gauge?

Seems electrical problems are the new gold mine on repair - the throw parts at a problem until solution is found is Mfg idea of fix . 
 Stop / Start light comes on on my 2015 Cherokee at odd times 20 miles of driving 5 miles next time , Light goes out when restarting only to show up again in xx miles . 
 Asked dealer about it back when under warranty - said they checked - no problem they could see . Once out or warranty and asked again said $200 to $300 to fix IF it was ?
  Every once in a while if you energize it manually - a notice of LOW battery - charging , low voltage , not in service at present comes up in display .