So I just went to use the wife's 01 and it cranked slowly. Looked down at the voltmeter and it's a 0. I have a 99 with a good alternator but looking quickly online seemed it wouldn't work. Ran to NAPA quickly right before they closed. Their computer says 01 is compatible with 01 only. So I had them order it so I can pick it up when they open tomorrow. Now I'm trying to make sure the alternator is bad.

Does anyone know what's so different about the 01 alternator? Are the connectors different or is it an amperage difference? Right now I'm troubleshooting.

 

Never mind. To answer my own question the 01 has just a single connector with two wires that plugs into it. The others have that weird rubbery thing with like three leads attached.

Something is strange though. I unplugged the connector from the alternator and checked the continuity from it to the green wire at the distribution center and my meter is fluctuating rapidly from OL to 0. Never had it do that before. It does not do that if I just touch the leads together.

And to clarify my initial post the gauge is around ten before starting, then it rises slightly for the first 10 seconds then it drops to 9 which is the lowest it reads. And with the meter on the battery the voltage is quickly and steadily dropping while it's running.

 

Doing some searching the alternator for 99-00 looks just like the one I removed from the 01 same plug and everything. Now I'm not quite sure what the difference is. Sucks because I have one on a 99 that I was going to use.

I got the alternator out last night and I'll have it tested before I pay for the one I ordered. Does anyone know of anything else that may cause the alternator to not charge?

 

Yeah if its covered with antifreeze from a leaking hose it will flake out to around 9v.
There may be other things.

 

 

A bad voltage regulator can cause the alternator to appear to be bad. I'm not sure if the 99 and/or 01 use an integrated (into the alternator unit) or not, but the earlier (at least 96 and prior) have the regulator in the computer.

The bench test should be informative.

 

The late model XJs are regulated by the PCM as well. I just looked through the part numbers on RockAuto and, sure enough, they show different part numbers for 01 than they show for 99-00. I thought it might be a differentiation in current specs, but the parts show the same amperage regardless.

 

Well the local NAPA doesn't do bench testing. Bought the new one if it stops downpouring I'll try to get it installed tonight. It was actually really clean for having just over 215,000 and 17 years old. The Jeep still has the splash shield and it really helps keep the engine and bay clean. Even though I'm in CT and it's been through some neadty winters there was no rust at all on the bolts. Everything actually looked new. The alternator was a little dusty that's all. And I looked at the one on my 99 and it also has the same looking connectors so I'm not sure what's different.

 

Got the new alternator installed. Everything is good. Output on the alternator was stated 136 amps. Running at 14.18-14.20 volts according to my meter. That was the initial run. It did drop some on the gauge after a bit but the battery was low at first. I didn't put the meter on it again but I would guess it settled around 12 volts.