01xj gauge says alter. is not charging

On my buddies 01xj the gauge says its not charging right we took the alter. off and had it tested, was told it works fine. changed the cables nothing,
I cant figure it out, i have 2 jeeps 91xj and 89yj and nothing like this has ever happened to me.

I'm lost

any help would be awsome

Bench testing is not always conclusive.

Take a meter. Use DC volts, 20 volt range if meter is not autoranging. Put one lead on each of your battery connections. Run engine at high idle. Should have approx. 14.4 volts. This way, you'll know for sure if the alternator output is acceptable.

Cleaning and freshening all connections electrical is never a bad idea.

Voltmeter on battery like birchlake says. Not running should be 12.5 or so, running 14.4 or so. No change, no alternator.

I agree with the previous advice, and I'd add a little to it. Make sure it maintains ~14.4 volts after you add as much load to it as you can. Fan on high, head lights on, etc. It may dip a little, but should still be able to keep up.

Getting a few posts lately that the Nippondenso alternators with the PCM charging control will report OK when tested at parts stores but are in fact bad.

It would appear that the parts stores testers, at least some of them, can't handle the late model alternators OR the people testing the alternators aren't using the equipment properly.

interesting i will check this out

thanks alot
ill let you know what happenes