After sinking my Jeep in a muddy hole a few weeks ago I had trouble with the alternator not charging so I whipped it off the motor and as I suspected the problem was just a simple case of the brushes sticking due to mud. Luckily a quick clean up resurrected the alternator but at the same time I discovered the brushes had very little wear left (perhaps only 1-2mm) and the bearings felt less than perfect so I knew the repair was only temporary.
Fortunately I have an alternator from a 1998 XJ that is a very similar unit but with some subtle differences to the terminals at the back. I think the sought after Grand Cherokee 136amp unit is the same too?
This is the alt from my 2000 XJ which according to my factory build sheet produces 124amps-
And this is the alt from the 1998 which google suggests is a 90amp unit-
My plan is to swap the bits at the back end over to make the 98 unit a temporary fit into my 00 XJ while I rebuild the 00 unit with new bearings and brushes. I have found that to do this I only need to swap the rear cover, the positive post insulator shroud and the component that the 2 pin plug is mounted on.
1st step is to remove the insulator from the +ve post. This is just a case of unscrewing the 10mm headed nut and then lifting of the plastic shroud.
Then you can remove the cover plate by removing the 3 nuts and 1 screw/bolt that retains it. These all have an 8mm head and are circled in this picture-
The cover plate may need a little persuasion to come off due to dirt and corrosion but it is only held on by friction once the +ve stud insulator and the four circled fasteners are removed. Once the cover is off you will find this-
The large red bit in the middle is a cap to keep dirt and water out of the brushes and is pretty effective as long as you keep out of really deep water. Pop the red cover off the brushes then remove the brushes by removing the 3 screws circled in this picture-
The screws require a Phillips #2 bit, not a pozidrive!
As you can see here, the brushes are worn badly and when new probably protrude 10-15mm.
Now you are at the stage where you can remove the plug that will allow you to use the pre-99 alternator in your later XJ. With the brushes out of the way the component is only held by a final two screws. The component you are removing is drawn around in blue and the two screws are circled red-
Now you will need to strip down the earlier alt to the same point and rebuild it with the later components so it will be a straight plug in swap into the 00 and 01 Cherokee. The additional supports on the external casing can be left in place as they do not hinder fitting into the alt brackets.
Although this is a lower power alt it is fine for normal short term use while I further strip my original alt to identify the bearings prior to rebuilding it. Once it is done I will post a rebuild thread to show how in most cases you will be able to repair rather than replace a faulty alternator.
