Ok so I traded a car for my 99xj inline 6. It was in a crank no start condition. Previous owners didn't know what they were doing and said so themselves (they cut a whole in driver floor to get to crank sensor). Well I tow it home, swapped out a fuse and it started up and drove but alternator wasn't charging, check guages light come off and on through out 4 days and it stalls, back to crank no start. Fast forward 7 months. It starts now after replacing crank sensor, distributor cap and tip, wires, plugs, ignition coil and pick up coil. New battery wiring etc. But the alternator still isn't charging. I asked the previous owner and they said they replaced the alternator (looks new) but they guessed how it was wired because days went by between removal and reinstall. So who can give me DETAILED wiring for the alternator? With pics, this is my first xj and I've looked up alternator wiring several times but I'm confused because it seems like everyone's is different (probably just me lol)
Currently they have a plug going from the loom to the back with 2 wires, but some threads said there's suppose to be 3 wires from the loom that plugs in the back and they have a thicker gauge wire going from the stud on back of the alternator to the negative battery terminal, which is why I'm lost. Should the thicker gauge wire on the stud on back of the alternator go to either the PDC or the battery positive with fusable link not the negative terminal?!

 

best thing is free download service manual from this site, look up member cruiser54 website, or google other places

I cant remember what the wires do, but it is regulated by the PCM, so if its been hacked up, you need the circuit diagram, or pics

You might get lucky and another member post pics, but you need the manual for these vehicles

 

Just went through this on another thread, but apparently it’s common for alternators to stop working after prolong sitting, and the cause is dirty brushes. To check, disconnect the 2 field wires and check the alternator side with an ohm meter. If it’s super high , aka open, there’s your problem. Also an easy fix with cleaning or replacing brushes, just 3 small nuts hold the back on and the brush set is right there, remove and spray it out
yes there’s 3 wires but the third is just a ground to the frame or batt
And gosh, yes, the positive post of the alt goes to a fusible link and then over to the fuse box

 

I just replaced my alternator a couple of weeks ago, so here are some pictures that might be helpful for you. IIRC, there are a total of 5 wires that need to be connected. The main positive terminal, two that attach to the alternator case, and two that attach to the back of the alternator. I'm not sure on the exact terms for each wire, so forgive my generic descriptions.

 

Just FYI ladies & gents

OEM alts all seem to die at once aged 27, like all the famous rock & rollers.

The diodes fail and they are done

I have about 8, and I stripped them all down, so I have 3 working ones

Its true the brushes may also be worn out, or one or more stuck back in their retaining spring

The Chinese made replacements have poor quality diodes

Maybe the expensive replacements have better diodes, one would hope so

 

[QUOTE=IJM;3725826]I just replaced my alternator a couple of weeks ago, so here are some pictures that might be helpful for you. IIRC, there are a total of 5 wires that need to be connected. The main positive terminal, two that attach to the alternator case, and two that attach to the back of the alternator. I'm not sure on the exact terms for each wire, so forgive my generic descriptions.


I think one of those nuts on the factory connector has no connection, all it does is offer mounting stability if that. the other nut is a supplementary ground. The case is grounded when you bolt the alternator in anyway but that ground is just insurance. The two smaller connections are the field and then the B+ output is the big main post on back that goes to the fuse block via the fusible link. So, 3 connections plus a supplementary ground maybe. Personally I’ve never seen one of these with a bad diode.

 

According to the Factory Wiring Diagram, your 99 is the same as my 01. There are only 3 wires to the alternator. 2 for the field excitation that are in a connector with 2 flat sockets...and one primary output wire that feeds the battery and PDC. There are no other terminal studs or grounds on the case . The pictures that IJM posted look nothing like my 01, and my 01 matches the 99 wiring print. If they bolted your primary output to the block...its a good possibility that your alternator is damaged.

 

Okay so I have the Haynes manual which doesn't help with my confusion. Ignore my awful hand writing

This is what I'm seeing on the Haynes Manual
[img alt="The previous owner had the wire I marked with yellow going to the neg post on battery
The plug has two wires coming from it DK GR & DK GR/R, I know DK GR/R goes to the ECU. "]https://cimg9.ibsrv.net/gimg/www.cherokeeforum.com-vbulletin/720x1600/screenshot_20250126_154320_2_fdf135743824023e3bd84 df0820b3155f57708e3.png[/img]
The previous owner had the wire I marked with yellow going to the neg post on battery The plug has two wires coming from it DK GR & DK GR/R, I know DK GR/R goes to the ECU.