Electrical issues.....

I have a '97 with the 4.0L and the aw4, I have ocassionally had voltage spikes for the past say 3 years. The first few times I had it I just thought that it was an alternator issue, so I installed a new bosch alternator and a optima. Problem solved, for a couple of years, then the same issue came back 10x worse now. Gauges go nuts, everything electrical speeds up or gets brighter, engine runs like a champ, but it throws off the transmission shifting.
So I replaced the POS bosch alternator, that was no longer under warranty, with the V8 ZJ alternator, works great; but still have the same problems. I replaced the computer, same problems. Optima is still good. Cleaned all power and ground wires except for the end attached to the block because its a PITA to get to, shot it with electric parts cleaner. I next plan on replacing the belt cause it slips when the A/C comes on, and the grounding strap that runs from the firewall to the block. Have I missed anything or is there anything else that I would need to check??? This is a DD, and I have too much invested to give up on the thing.

still sounds like a ground issue....

After nearly toasting the red top, I finally found the time to check out the other end of that grounding strap. The universal that we sell at the store wouldn't fit, so I had to make one with 0ga wire. Works great no dimming period, no spikes, and no shudder when the A/C kicks on and off....

Amazing how often automotive electrical problems come back to shonky grounds, isn't it?

glad to see you got it fixed.....

Well, as usual I spoke too soon, it started back up on Saturday, after say a week and a half of no problems..... Waiting for it to trash everything under the hood, so I am really starting to freak out. My only other thoughts that it could be are the main connections to the battery even though they look good. Is this a possibility? My date and stroker money are now going to keep this thing running, need help quick...

is there a voltage regulator? battery terminals are cheep, made a hell of a difference on my mj

The voltage regulator is in the computer, and I replaced the terminal ends and swapped the battery from my boat in last night and within 3 miles I had the same result. The only common thing that I haven't changed are the battery leads..... So for a recap swapped computers, alternators, ground straps, batteries, terminal ends, and still get the same result. It almost has to be the leads, if anyone has any suggestions let me know, if not upgrading to 5-90's wiring setup.

Okay, so round 4,329.... I have gotten 5-90's kit installed, many thanks by the way. I have driven it in stop and go conditions, high speed, lights on-off, whatever I can and not even a wiggle from the volt meter. Hoping that I have found the cause of all of my problems. Will keep you posted, now back to spending money on the stroker build..... I hope!

Sounds great. 9 year old cables sure can look good, and act up horribly.

If there is anything I've learned about cars getting older(starting with a '66 Mustang,) Detroit has improved engine life, but done nothing for the wiring in the last 50 years. There's just lots more of it.

JTwthaXJ said:

Okay, so round 4,329.... I have gotten 5-90's kit installed, many thanks by the way. I have driven it in stop and go conditions, high speed, lights on-off, whatever I can and not even a wiggle from the volt meter. Hoping that I have found the cause of all of my problems. Will keep you posted, now back to spending money on the stroker build..... I hope!

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You're welcome. Yep - sounds like cleaning up your grounds and replacing your mains solved the problem! It usually does, from what I'm told...

Started to get some flickers this afternoon, all I have really done since the other day was wash the Jeep. Any ideas as to why it would start this all over again? Really getting tired of this...

JTwthaXJ said:

Started to get some flickers this afternoon, all I have really done since the other day was wash the Jeep. Any ideas as to why it would start this all over again? Really getting tired of this...

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I'm fairly sure I let you know how to ensure good ground contact with the chassis - did I? If I did, did you?

If I did not, please let me know. I've not done illustrated instructions yet (I should,) but I can walk you through it. Quite a lot of automotive electrical complaints come back to shonky grounds...

I am pretty sure that you did, I took 180 grit sand paper to each place where a ground makes contact then rinsed it with electrical parts cleaner, then did the anti-corrosion stuff before I bolted everything down. I pretty much got through the paint everywhere that the grounds connect. Still taking suggestions, I am 99% sure that I did everything the way you said.

Thanks,

JT

If your 97 is anything like my 96, the PCM reads the input voltage to the PCM and adjusts the (regulates) the alternator output accordingly. So if the PCM reads low voltage (or excessive resistance in the ground circuit) it increases alternator output. Find the power *in* for the PCM, put a volt meter on it and shake the harness. If the voltage fluctuates you may have found your problem. Any kind of resistance in the PCM power in circuit, is going to cause the alternator output to increase. Low voltage to the PCM, increases alternator output (increases the grounding for the field windings)
The voltage *in* to the alternator field windings is constant battery voltage, the alternator is regulated on the ground side of the field at the PCM, so any kind of short in the alternator to PCM field wire will cause a spike, or runaway alternator. Check the field ground wire between the alternator and the PCM for a leak, wiggle it and see what your ohm meter says.
The battery temperature sensor is also worth a look. This also has some affect on voltage output.

Subscribing to this to see what you come up with. I'm getting ready to install the wiring kit f/ 5-90 in hopes that it will cure my low/fluctuating voltage issues on my '96.

At the very least, my cables are pretty worn out and corroded... so it's great insurance and appears to be money well spent.