Zfrye2959

Hi everyone! Hopefully I can get some good insight here! I have a 2001 xj that is having voltage problems. Here is what's going on, along with the steps I've taken to solve this problem:

I installed a snorkel a few months ago and decided to test it out. I got pretty carried away and went as deep as to nearly dunk the hood. I know this was a BAD IDEA, so there's no need to badger me for that now lol. I'm paying the price With this 3 month struggle to fix electronic problems.

Anyway, the drive home I noticed my headlights were rapidly fluctuating brightness, though the fluctuations were extremely subtle and hardly noticeable, to the point where I was wondering if my eyes were just playing tricks on me at first. They weren't. About a month ago, I came to notice my car wouldn't start. I tested the alternator and battery, and determined that the battery wouldn't hold a charge anymore. So I replaced it. The next day, car still wouldn't start. So I figured I must have tested the alternator incorrectly and replaced that too. However, I was still having the issue of fluctuating voltage. After reading some forums, I learned that the voltage regulator was inside the computer and that you could bypass it with an old dodge regulator. So, I did. Only to STILL have the fluctuating problem, except now it's charging and fluctuating between 15.1-15.5 volts. I HAVE checked all my ground connections and they are all cleaned up and making solid contact. My last resort to try is to remove my power capacitor from my sound system. I'm wondering if the high voltage that the new regulator is making the alternator was too much for it, and now maybe the cap is having a hard time discharging quick enough or something.

So, to recap, here's all the steps I've already taken:
Replaced battery
Replaced alternator
Bypassed computer VR with external regulator ( has a freshly sanded ground too)
Checked all main ground connections

If anyone has any ideas or maybe has had this issue before, please do let me know how to fix this problem before I cook my electrical system!

97grand4.0

How about the headlights themselves? 15.1 - 15.5 is too high, but the range of .6 is ok.
How about the headlight plugs? Is it both headlights? What you really need is to have a voltmeter to verify some of what you see with the lights, don;t just go by the headlights. Actually advanceauto has a free test they will do, have you tried that? they have a cool LCD printout that will check for diode problems, battery loaded and unloaded, alt loaded and unloaded.

Zfrye2959

I failed to mention that my dash lights as well as my some light fluctuate as well and only when the jeep is running. I do have a volt meter and I realize that 15v is too high, I'm trying to figure out why it's charging that high. I'm wondering if the external VR that I used is just programmed too high. Its for a 79 dodge.

Zfrye2959

I will give advance auto a try though for sure.

97grand4.0

With the external regulator in play, you should be completely bypassing the ECU internal voltage regulator., I think. There is a battery temp varistor sensor under the battery in the tray that I replaced on mine with a 50k resistor, and I charge around 14.9 all the time no worries.
Have you made absolutely sure the connections, battery, alt, ground, B+ are not loose? How about the field connecting plug on the Alt? It the field connection is intermittent that would make it erratic in charging. I am going to lean toward a bad connection if it only happens in motion.
I would still take it to advance for the free check, they will give you a paper printout showing the diodes , but, it sounds more like a loose connection or a part that flakes out on vibration.

Zfrye2959

I have checked all the connections that I'm aware of, although I didn't know about the variable sensor under the battery. I will ohm that out. Do you know the typical resistance I should read there? And these fluctiation happen when the vehicle is on regardless. It doesn't need to be moving. One other symptom that I notice is when I roll my Windows up, my power capacitor energizes a relay and cuts my music out temporarily. That would lead me to believe there's too much voltage getting to the cap and maybe that means I have a short somewhere. I am truly at a loss which is sad because I'm and electronics technician lol... Smh

Zfrye2959

Also about the intermittent factor... The only thing intermittent about it is that there's no fluctuation in voltage when the car is turned off. When it's on and the alt is charging, the fluctuation is consistent. It is bright then dim and back 2-3 times per second, so that wouldn't scream loose connection to me. I do wonder about that varistor though being as its under the battery and I had water Damn near reach the hood..

Turbo X_J

Faulty ground.
Doesn't sound like the regulator on board the PCM is faulty, change it back & proceed from there. No need to fix stuff that ain't broke yet. 15V+ will cook your battery in short order.

Zfrye2959

How would you go about checking for another faulty ground? I've checked resistance to the chassis, engine block, and alternator. Is there somewhere else I should be looking?

mikesignal

high voltage usually means you have a short or wire going to ground somewhere..... 15 volts is too high. I agree put it back to OEM start off from there....you mentioned the window issue. The door jam is notorious for cracked wires....definitely go back and check all connections, ground and positive. Wiggle the wires at night with the lights on. Check connections at the fuse box too.

Zfrye2959

I will check for broken or cracked wires... But the cap relay actuates when any window is rolled up and only when the window touches the top of the door frame. I will remove the external reg from the system for now, but I seriously have no clue what's causing the instability. Like I said before it's not an intermittent thing, the voltage fluctuates consistently back and forth a few times a second so I really doubt it's a ground or wire problem. There's gotta be a bad component in the charging system somewhere. Anyone know where I can get a detailed schematic for an 01 xj?

97grand4.0

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So,this only happens with the jeep running? If you can roll the windows up with the key on, engine off, and everything is normal, then I would def be looking at the charging circuit, the B+ wiring from the alt to the rest of the car, the B+ going down to the starter solenoid and the other one that bolts to that for bad, loose worn connections, the 2 wires that go to the field magnet on the alternator (this could be 2 little 5/16 nuts, or maybe a plastic connector plug) , the B+ that goes from the alt output to the fuse block under the hood, this may be a fusable link that is going south...
Absent any of that, I would say the pcm where the volt regulator resides, but seemingly you replaced that.
I would also be looking again at the so called sound system and this bypass cap you put in, try bypassing that, check connections, (is the 'bypass cap' itself bad>>>??????)