Electrical issues

Hey,
Just picked up my first XJ last night. 30 minutes into my drive home my headlights started getting brighter then dim. this went on for 20 miles off and on then i noticed my volt meter was going from 14 ish to 15-16 then 12-13 ish. once i noticed that my whole gauge cluster went crazy the check guages light came on the volts were maxed out headlights full bright the speedo and tach were all over the place about 10 seconds went by then back to normal. it did that twice more about 10 minutes apart. once it settled back down it would be back to just a little high on the volts and the slight flicker on the headlights. the last 20 minutes of my drive were uneventful. I tried to get codes via key and trip button but didnt show any even tho the check eng light is on. the abs light came on during the whole wig out also and has remained on. initial thought are alternator and or battery. I will do some more trouble shooting/autozone trip for diagnostics this weekend.
97 xj 4.0 4x4 4 door 205xxx miles.
Thanks for your help in advance

Not as familiar with those year XJ but I'd check the headlight switch and see if the harness looks ok. At least on older XJ they tend to melt.


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If the dashboard gauge shows low voltage you typically have an alternator issue. If the dashboard gauge shows high voltage you have a connectivity issue: damaged/loose/corroded battery cable lugs, loose or corroded/dirty wire connections ( + or - ), or internally corroded cable/wires. Perform routine maintenance of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Battery terminals and battery wire connectors should bright silver, not dull gray and corroded. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, wire brush, and clean until shiny the cable/wire ends and whatever they bolt to.

Have the battery and alternator Load Tested inside a test machine. Handheld testers are inaccurate and will often pass marginal alternators and batteries that would fail under a load test.

Thanks for the info Tim. I stopped by O'Reillys yesterday, they said my battery is shot. I have a new optima coming in the mail. until then i will swap out my cables because they look like crap anyway and arent helping my situation. I also noticed yesterday that my jeep wasnt down shifting it would get into 3rd gear and stay there so now im manual shifting it. I read that the throttle position sensor can have issues if the voltage is all jacked so i will see when i get a new battery.

Well, new optima red top installed drove off made it 2 miles and it started again. Drove right to O'reilleys and they said my alternator was shot it was sending 18 volts out which was verified by my gauge and multi-meter. I took out the alternator and brought it back for testing before i bought a new one. Tested perfect, thinking this was strange i brought it to autozone also...tested perfect. I then went back to oreilleys and picked up 5 4 gauge wires and new brass terminals. (wish i could have went with 5-90's setup but i couldn't wait for them) Anyway got them all installed and drove around about 10 miles and i dont have any issues! Pretty excited, hopefully it stays nice to me.

Alternators can come and go if the brushes are almost gone, and then die for good, so don't write this off as solved just yet.

Also something the stores missed is that the voltage regulator is not in the alternator for your year, it is in the PCM computer, so if the alternator is testing good and the problem returns I have bad news, you need a year specific PCM from what I have read here over the years with right accessories, manual versus auto transmission...., right engine size etc.

Let's hope the problem was a wiring problem to the PCM, or PCM to alternator, and is fixed!!!!

Yes lets hope, the guy at O'reilys was arguing with me about the voltage regulator being in the computer, glad I was right and I hope that won't be an issue. Drove it to work today and its still holding strong. Now on to the intake air temp sensor.

All of what you have described can also be related to the ground wires, i.e. corrosion.

Good Luck

well...after countless hours and beers i think i got it figured out. after starting this electrical nightmare journey with a new battery that fixed the problem for a few days, then took out my alternator just to find out it wasnt the problem then ALL new cables then the jeep had no issues...for a week. my alternator started over charging again and gauges start going all wonkey. i took out the old good alternator and replaced it with a new one, made it about 20 feet before it started acting up again. Started looking for shorts, the only thing i could find pulling power was for the interior lights. So i came back on here and seen old mans post about grounds. Went back at it and grabbed the dremel, i ground down to bare metal on all the grounds and walla!! no issues so far, ive only gone about 50 miles but it seems promising. thanks again for your help.

Great trouble shooting here. Did the ground wires solve the problem?