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Jeep Cherokee Charging Problems - HELP!!!!

This is a discussion on Jeep Cherokee Charging Problems - HELP!!!! within the Automotive Support forums, part of the Tech Support Forum category. First off, I am not new to auto repair. I rebuild vw beetles in my spair time and have been

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Old 01-20-2006, 08:44 PM   #1
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First off, I am not new to auto repair. I rebuild vw beetles in my spair time and have been repairing cars and trucks most of my life.

That gbeing said, I have a problem with a jeep that has me dumbfounded.

I have a '93 Jeep Cherokee Sport, 2wd, at, etc... About 2 months ago, when ever I cranked it, the volts gauge sat at 12 for a few minutes to 30 minutes and then jumped to 14. Didn't think much about it, maybe the needle was sticking. Then, of course, it went dead.

I had all the usual suspects tested. Took the batery and alternator to be tested, both were fine. Replaced the entire battery/starter harness, $92 by the way, no difference. Took it to the local Jeep dealership and let them run an $82 diagnostic on it, they said it was the best running '93 jeep they ever saw and then it died again on the way home from the dealership.

Someone mentioned the voltage regulator to me. It's part of the main computer, not built into the alternator like most "Normal" cars. Wouldn't a factory diagnostic catch that?

Please someone give me a clue how to fix this. I love this Jeep and don't want to get rid of it.
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Old 01-21-2006, 05:18 PM   #2
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I had a similar problem a few months ago w/ a 94 Jeep GC Laredo. It turned out to be the alternator, but as of a couple of weeks ago the battery seems to be low ( a fairly new optima ) . Would be interesting to figure out if it's a cpu issue .
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Old 01-21-2006, 08:31 PM   #3
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when I had the alternator tested, at first they said it was bad because it was only showing about 11 volts, so they put a brand new one on their machine and it charged exaclty like my old one, about 11 volts. There was a sticker on the back of the new one that said it was externally regulated, so they looked it up and found that it's built into the computer.

One thing I noticed, every time I disconnect the battery, it seems to do fine for about a day or two, charging normally and all, then it starts all over again. It's kind of like disconnecting the battery resets something in the computer but only temporarily.
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Old 01-22-2006, 05:01 PM   #4
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It should set a trouble code if there's a problem with the driver in the ECM. I don't have my manuals in front of me now, but let me know if you still have the problem and I'll look it up for you. I'll need the first 10 digits of the VIN.
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Old 01-22-2006, 05:43 PM   #5
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13.6 Volts is minimum for a charging alternator............................
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Old 01-22-2006, 06:06 PM   #6
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A few things to look at:

1. Some of the newer Jeeps had a battery temp sensor in the battery tray to monitor the battery temp and lower the charging Voltage when the temperature hits a high point. Check to see if yuor vehicle has anything like this and if it is acting up.

2. Poor connections and too much Voltage drop can cause problems. A simple Voltmeter can test for this. You can probably find Voltage drop testing info online.

3. Bad, broken or missing grounds are common problems as well.

4. And of course faulty alternator/regulator can also be a problem.

Expect to have between 13.8 - 14.5 Volts at the battery for a properly charging system.

Look this link over for more info:


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Old 01-23-2006, 05:35 AM   #7
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thanks for the tips everyone, mullet man, I would say your correct, but the parts guy tested a brand new alternator straight out of the box and it only charged 11 volts, the regulator would be what tells it to charge more than that.

JamesO, alot of good info there, thanks. I'll check on the temp sensor. I put a voltmeter on it and one day it tested great, next day, horrible. the grounds shouldn't be the problem, I replaced the battery "harness", which is all positive and negative cables and connectors, and checked to make sure everything was getting a good connection. It acts like a bad alternator, but it has tested good at 3 different places, Advanced Auto Parts, O'rielly, and AutoZone. Since the regulator is external from the alternator, this is what I am guessing it is.

I will spend a week tracing wires and cables just to be sure, if nothing is found, I'll cut my losses and sell it. I only paid $500 for this jeep and this is the first major problem I have had with it in 3 years, so I'm not complaining.

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Old 03-04-2006, 02:39 AM   #8
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I dont know if youve pressed much more foward, bkut I have been having the same problems. I replaced the ECM(which was a good chunk of change) and still had no fix. I was curious what might have fixed your problem
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Old 03-26-2006, 01:44 AM   #9
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an alternator can very in how it charges i have seen them run fine one min. and then draw high amps in a nother so i would repace it and see if i fixes it
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