92 YJ Charging System

[MRFR2CWO4]

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

[TJS27]

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 ain’t cheap. Alts are.


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[JPNinPA]

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

[MRFR2CWO4]

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.

[JPNinPA]

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 don’t 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

[yj93ben]

Where is the "battery temp sensor" located? What does it look like?

[superj]

Its a button in the middle of the battery tray, i think

[JPNinPA]

Not certain what year the sensor wss introduced.

Never look down on anyone unless you are helping them up - Jesse Jackson

[MRFR2CWO4]

This was solved.... Thanks for all the advice. Replaced the alternator (and battery was also requiring replacement) and have not had an issue since.

[superj]

good deal.

[Gennybro]

yehawww