1. Exclamation 92 YJ Charging System

    Hello Jeepz Forum Members,

    I have a '92 Jeep YJ, 4.0L. My voltmeter in the dash is reading low, and after replacing the battery (needed to be done anyway), I am still having problems with the battery not receiving enough voltage to charge. The good folks at O'Reily Automotive connected a test rig, and informed me that the voltage regulator is bad. This voltage regulator is a part of the PCM (ECM?) and I am wondering if anyone has replaced one themselves and what is involved, or do I have to take it to a dealer in order to have the replacement computer flashed? Again, if I am to trust the test that was conducted, the alternator is not bad -as I would assume that their diagnostics would have indicated such. Any advice on where to start to get my rig trail worthy again?

    Thanks in Advance,
    RSR

  2. #2

    Re: 92 YJ Charging System

    Quote Originally Posted by MRFR2CWO4 View Post
    Hello Jeepz Forum Members,

    I have a '92 Jeep YJ, 4.0L. My voltmeter in the dash is reading low, and after replacing the battery (needed to be done anyway), I am still having problems with the battery not receiving enough voltage to charge. The good folks at O'Reily Automotive connected a test rig, and informed me that the voltage regulator is bad. This voltage regulator is a part of the PCM (ECM?) and I am wondering if anyone has replaced one themselves and what is involved, or do I have to take it to a dealer in order to have the replacement computer flashed? Again, if I am to trust the test that was conducted, the alternator is not bad -as I would assume that their diagnostics would have indicated such. Any advice on where to start to get my rig trail worthy again?

    Thanks in Advance,
    RSR
    Hmmm. I had same issue with only 9v then surges to normal. It was alternator. The alternator from what I understand has a built in regulator that gets its que from pcm to open the regulator when a certain voltage is hit from the battery. Ie lower than 13 volts or so.
    I would get a second opinion myself.
    PCM aint cheap. Alts are.


    Sent from my iPhone using Jeepz.com mobile app

  3. #3
    Join Date
    Feb 2009
    Location
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    Re: 92 YJ Charging System

    PCM is not hard to replace.

    Definitely verify the alternator is good.
    Id also check wiring as corroded wiring may cause a voltage drop.

    Typically voltage goes high like 19V when the regulator fails.


    Never look down on anyone unless you are helping them up - Jesse Jackson
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  4. #4

    Re: 92 YJ Charging System

    Thanks @JPNinPA and TJS27. I suppose I will remove the alternator and take it for a thorough test, since this is not within my scope of ability. Appreciate the advice.

  5. #5
    Join Date
    Feb 2009
    Location
    Dayton Ohio Area
    Posts
    6,184

    92 YJ Charging System

    Also consider there is a battery temp sensor under the battery. If it goes the battery will not ve charged to peak voltage.


    There may bean external regulator that could be added. Never did it myself.

    However I did have a F150 that occasionally would not start. I noticed the dash voltage gage pulsating and found if you shut it off when that is happening it acted like a dead battery. It would take some time before it would start. Found the brushes wore down and were shorting together. Cheap fix. They dont make alternators like that anymore.



    Ill end with checking and cleaning all contact points on the big three including grounds.
    Check the wires for corrosion.
    Think about this: Changing the power and grounds with new clean contact points will do you well even after fixing any issue.


    Never look down on anyone unless you are helping them up - Jesse Jackson
    Last edited by JPNinPA; 09-22-2021 at 11:03 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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