AC question
 

1997 Cherokee Sport, 205,000 miles and going strong -- Whenever I turn on the defroster I get a super loud rumbling noise (not a squeal or screech). I assumed it was the AC compressor so I unplugged it. It still makes the loud noise, and only when either the AC turned on directly or through the defroster, otherwise it is quite. I have no idea at this point what is going on. Anybody have any ideas?

Disregard - got it figured out
 

I did not realize that there are two electrical plugs that need to be disconnected before the compressor is silenced. I have a new one coming in. Any tips on installation? thanks

Document, document, document... if you haven't done one of these before just take your cell phone and before you remove anything in each step, take a detailed picture. That way you can look at them in reverse when you're putting the new one on.
Before you start the process, you need to have the remaining refrigerant in the system properly evacuated as it's illegal to let it just go into the atmosphere.
Are you certain that you have a bad compressor? One test you can do in the fuse panel under the hood is temporarily swap the compressor relay and the horn relay. Then try your horn, if it works then it's not just a relay causing the issue. There is also a fuse next to the relay for it, check that one too. It is labeled on the under side of the cover. Be sure to swap the relays back to their original location after your test.
There may be a better one online somewhere, but this will give you a general idea of how it works. And on our XJ's it doesn't get any easier as a DIY than this....