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Good Alternator, almost no charge

redrider2911

NAXJA Forum User
Location
Yakima, WA
This is my first 91+ xj. 1991 limited 4.0 AW4. No charging or light modifications done. Someone did add a trailer light kit to it.

2 Weeks ago a took a long road trip and notice my voltage almost in the red and the check engine light came on. I've had alternators die before but usually bad brushes and lots of squeeling. I reved up the engine a little and it would go back up to 14 volts. Then 15 minutes later it would drop back down again. So I reved it up again. As time went on I had to rev to higher RPMs to get it to kick back in and the voltage would drop sooner and sooner. Until the point I had to stop.

K so I replaced the alternator, tested the battery (it was still good) and cleaned the post and connections on the battery.

It drove fine for a week then all of a sudden the problem came back up. I payed attention more to what was going on and noticed my AW4 also seemed to go into some kind of limp mode.

All the grounds are there, intact, and clean. Am I dealing with a regulator problem? I know renix had regulators built into the alternator. Is there a fusable link somewhere Im missing?

Thanks for any help in advance.

Oh, also. I believe I have a bad or dirty NSS. I have to fidget with the shifter some times to get it to turn over. I also found out this vehicle has a stock alarm.
 
Is your belt tight? Maybe your "good" alt is not working like it should. Had this happen on my Renix shortly after I got it. Tested fine, but would not charge. I would get a replacement and see if that fixes the issue.
 
I just got the battery charged up enough to get it started. I had 12 volts on the small terminals on the back of the alternator. Thats good news then right? Not a bad v regulator in the PCM... This alternator is out of my brothers 94. Come to think of it he had problems recently but I thought it was a bad battery. I cant remember now its been so long since he ran his Jeep. lol

I heard there was a fusable link somewhere I should check... Kastein or 5-90? any ideas?
 
I'd verify your exact charging with a meter at the battery. A healthy system should be in the 13.5 - 14.0 volt range with a healthy battery and a healthy charging system.

The voltage regulator for 91-01 is in the PCM

Freshening all engine grounds (can't tell a thing by looking at them) is never a bad idea.
 
Already did. Volt meter reads 12.3 volts when running.
 
The block ground cable is the usual suspect here, the one attached to the stud sticking out of the side of the block over the oil filter housing. make sure it's clean, also the surface of the block under the nut on that stud as well. you can check your cables with an ohm meter as well, they may show 12v but if you have a lot of resistance the juice isn't going to be enough to charge the battery. if there is corrosion on the ends of the cables chances are it crept down into the wire insulation, once that happens they are pretty much useless.
 
Ok. So I was going through and reinstalled the alternator. Went to put the belt on and noticed it had been wrapped wrong this whole time. Instead of looking like this in the diagram on the fan shroud http://www.cherokeeforum.com/attach...g-out-serpentine-belt-belt-routing-tagged.jpg It wrapped around the ac, over the top of the fan pulley, then around the alternator, and strait over the the crank. So instead of having a full half a wrap around the alt pulley, it had less then a quarter wrap! Could this be the problem the whole time!?
 
it could have something to do with it, yes, but as long as the belt got good and tight it may not be your problem.
 
Got the new alt hooked up and everything is good... At least for now. tested the old alt at NAPA and it read good.
 
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