Does your car have closer or over 100K miles? Have you ever replace the ac clutch pulley or bearing?
When the ac clutch pulley bearing goes bad (you might get 100K miles before it dies), if you don't replace the ac clutch pulley immediately, the pulley will wobble whenever the engine is running, and it will make contact with the ac clutch coil ruining (damaging the windings) shorting it out.
At that point you will need to replace the ac clutch set (magnetic plate, ac clutch pulley, and ac clutch coil) or the complete ac compressor with clutch set.
You can check the ac clutch pulley bearing with the compressor in the car by removing the serpentine belt, giving the pulley a spin, and observing what happens. If it grinding, or is loose, or spins freely, or spins canted, or wobbles, then the bearing is bad, and you need a new clutch pulley. If you can see or feel it hitting something, then you waited too long, and the ac clutch coil is ruined as well.
If the pulley spins true, and smooth with a little drag (that should be the grease inside of bearing), then the clutch pulley should be okay.
The flat plate on front of the ac clutch pulley is the magentic plate. It moves in and out when the ac clutch coil is energizes to engage the ac compressor. If the gap/clearance between back of the magnetic plate and the front of the ac clutch pulley is/becomes too large, then when the ac clutch coil is energized, the magnetic plate may not move to engage the ac compressor.
There is a spec for the magnetic plate clearance. If I remember correctly it is between .015" and .030". Some people have suggested using a broomstick while the engine is running with the ac switched on to push the magnetic plate towards the ac pulley to see if you can force the magnetic plate to engage the ac clutch pulley. This may prove that everything is working, but that the magnetic plate clearance needs to be reset.
You need to buy an ac manifold gauge set if you are serious about working on your ac system. The little gauges that come on refrigerant cans is a joke.