Ok, heres the info I have to share, hope it helps:

My AC was not working and a loud noise was coming from the compressor so I removed the hub assembly to find the triangle with with 3 magnets had seperated from the circular disk, hence the loud noise.
I replaced that hub assembly to find that this fixed the noise but it was still not properly engaging all of the time. I figured I would check the bearing and go from there so I then removed the hub assembly and pulley, but bearing was fine, the field coil however was deteriorated and not working at 100% effectiveness. Wanting to avoid both having to buy an entire compressor AND removing the compressor and therefore having to recharge the freon if possible, I purchased the kit from the dealership that includes the pulley, coil, and hub assembly and replaced them all with the compressor still on the truck. This was hell by the way and I wish I would have bought the whole compressor (which includes all these parts I replaced already on it) and just replaced it all. Everything comes off easily until you get to the coil, and even the coil came off without too much trouble for me using a pulley remover tool. But not only was it a pain rigging the pulley remover to "press" the new coil on to the compressor, but the way the compressor is positioned, I did not have enough room to press it back into place directly perpendicular to the compressor and therefore kept pressing the coil back on at a slight angle to where it was not even and fully seated flush against the compressor. After a few attempts, I finally had to unbolt the bottom bolts of the compressor and loosen the 3rd bolt at the top and was miraculously able to fully seat the coil in the correct position. This might be more feasibly accomplished with the correct Ford "special tool" but if I had it to do over again I would not bother unless the compressor was removed and even then, for the $70-$90 or so more I could have spent on an entire compressor, it isn't worth the trouble to me...read on. Before putting the coil in place I noticed a tiny film of green residue on the shaft... this could be the dye from the freon, indicating the shaft seal could be leaking. This could also have something to do with why the coil had deteriorated and began malfunctioning... since I was not about to try and replace the seal without removing the compressor I decided to put it back together with the new coil, pulley, and hub assembly and hope that maybe it was a little antifreeze rather than dye or that the leak was minor enough not to be a huge concern for the time being until I could have time to remove the whole compressor and either replace it or replace the seal. So I put the pulley and hub assembly back on, torqued the bolt to the proper specs and tested it... it seemed to work fine and I was out of time and needed my truck for school and work so it would have to do until I had another chance to spend time on it. Well, a few days later the AC stopped working again, this was yesterday, so I have not looked at it again yet but let me just say that in the time I have already spent on it I could have replaced the compressor 3 times lol. So let this be informative to anyone needing to replace the coil, if you don't decide to replace the whole compressor then I would at least consider removing it first and not being a stubborn, hard headed goober like myself... it was a good learning experience, although a very painful one.

Basically, this is how it works (more or less, so no *** chewings for not being exact on technical specifics , unless of course I got something incorrect that indeed needs to be clarified :o):
The hub assembly has 3 magnets on that outer triangle and "floats" on the outer part of the shaft, not spinning with the pulley when the compressor isn't engaged. When the AC is turned on, the magnets in the coil are activated (I assume by electric current) and this pulls the magnets on the hub assembly, causing the hub assembly to lock in place against the pulley which turns the compressor shaft to kick on the compressor.

If yours is making a loud noise when engaging but is otherwise working fine then you might want to make sure you don't have too many spacers (the little washers between the hub assembly and pulley) on and check the clearance between the hub assembly and pulley when the system and truck are all off. Otherwise, depending on the noise, it could be something internal with the compressor maybe? If the clearance is correct then I, personally, am not sure I would worry too much about it if it is working fine otherwise. But of course, I don't know exactly how the sound is and haven't looked at your truck so take that opinion for what it is worth...

 

My compressor (97 4.2L) makes a rattle noise when off, but seems a lot less noisy when on, so if I read this correctly it is the clutch (bearings) going bad or did I miss something? and would it be feasible to spend the money for a new assembly that included the coil?

Thanks for your patience.

update looked at it again...the pulley spins while off, but it seems to free spin, catch (like the magnet) free spine, catch, free spin, catch, etc. is this normal. The noise actually sounds like its coming from the other side of the motor...?

 

It is going to spin and stop during periods as the compressor is kicking on and off as needed for the AC but it should be doing it when you feel the compressor come on and shut off. If for example, as soon as you feel the compressor kick on, the outer assembly hangs immediately or within 1-3 seconds and makes loud noises at the same time then something isn't right. It should be smooth in transition and not like the compressor is kicking on but a broken outer hub is fighting it. It shouldn't make an abnormal amount of noise and it should not constantly hang and catch within only a second or two between intervals.

If the outer hub is failing it is likely due to another problem causing it such as a bad bearing or bad coil. If you remove the single bolt (careful not to let the spacers/washers fall and get lost) in the center then the outer hub will pull right off and you can "usually" tell if the bearing has failed and come apart beneath that pretty quickly. If it is not the bearing and is the coil then don't even try to replace that without removing the compressor, and from my experience if you are going to buy the whole set that comes with the pulley/bearing/outer hub/coil then you might as well replace the whole compressor. If however you can somehow get away with buying and replacing the coil only then maybe it might be worth it, you will have to decide. Can still be a pain in the butt to press it on without causing harm to the compressor without the right tool unless you have other pullers and ingenuity in rigging something up your confident in...

 

I have a 2001 F150 supercrew lariat with the 5.4. My A/C compressor rattles when the A/C is off and I only notice it while the engine is idling but not sure if it happens while reving or driving. Anybody know if i have to replace the whole part? and if so how tough is it to do?

 

The answer to your question is already in this thread, please read the whole thing.

 

I have the same issue for a while but the noise will usually calm down after a second or two. However this morning started it it was louder than normal and then smoke. Shut it down and looked the serpentine belt broke I’m assuming that’s where the smoke came from. Did this happen because of the clutch seazing up I have not had the opportunity to really inspect it as I had to leave for work

 

I need to replace mine then. It's loud enough I have to turn it off when in a drive through. Anyone know what would cause the ac to stop blowing when on heavy throttle? I assume a vacuum leak either on the manifold or under the dash?