agitating alternator questions

alright, first let me say i can't figure this crap out and its driving me nuts cause my rig is just sittin on the trailer begging to be taken out. i bought a 89 xj 4.0 pioneer, with supposedly a 91 motor in it. the tranny was a 2wd tranny, but the jeep was originally 4wd. anyway, i took the tranny/tcase out of my 92, threw it in the 89 and swapped over all my suspension stuff, axles, springs, etc. ok, well, i finally got everything in and hooked up, but the alternator bracket was torn to peices and the alternator that the PO had on there didn't even look like it was from an xj. so i scrapped that and got an alternator and bracket for a 91. well, the bracket bolted right up fine and dandy, and so did the alternator, got the belt on and looked to hook the alternator up. there is a yellow wire and a tan/blk wire coming from the loom that were hooked up to a generic plug that was plugged into the orig. alternator. i disconnected the plug, but low and behold, on a 91 alternator there is a little black box that bolts to the alt. well i don't have this box, so i figured well i'll just get an alt. for an 89. ok, the alternator does not bolt up to the bracket that is on the block. WTF!!!??? so my question is, how can i make the alternator for the 91 work with the 89 wires??? there are two terminals coming off the alternator aside from the wire going to the battery. can i make this work or what? PLEASE PLEASE PLEASE HELP!!!

Your main problem is going to be that the alternator for a 91-up has no internal voltage regulator. The regulator is built into the Engine control computer. You're either going to have to jury rig an external regulator or find a different alternator that fits. Either that, or you'll need to figure out just how and why the older alternator doesn't fit the bracket, and modify one or the other until it does.

Actually, it shouldn't be too hard to figure out an external regulator. I think the Jeep alternator is a Delco, and with a little creative connector fabbing, you could probably find a regulator from an older model GM vehicle that would work. Or maybe a solid-state Motorola unit from the 60's. Regulators for alternators are pretty simple. Some, such as Bosch, used the idiot light as part of the circuit, but even that can be gotten around.

so what exactly does that little black box that bolts to the alternator do? I was thinking of just trying to figure out which one of those terminals that come off the back of it does and connecting the two wires coming out of the loom up to those? but if there is no internal regulator then i guess that wouldn't work. can you buy regulators at any normal parts store?

another question, are the brackets different for an 89 and a 91 since the alt. are different? could i just bolt the 89 bracket up with the 91 alternator and be done with it?

It occurs to me to wonder what fuel injection system you have with your 91 engine. Am I right in assuming that it was retrofitted to the 89 Renix system, not updated to the 91 Chrysler system? If the latter, then you do already have a regulator in your setup.

It could be that the oddball alternator the previous owner had put in was done for the same reason you are now having trouble - that is, that the 91 alternator wouldn't work with the Renix system, so he got a different one. You might consider reusing that one, if it fit and worked all right.

If you have an 89 alternator and 89 wiring, I think the best thing to try would be to find another 89 bracket and hope that it will fit the engine, which it is likely to. Otherwise, you will need to bone up on your alternator wiring, find out from your favorite local auto parts dealer what is available in the way of regulators, and get creative.