Start out by checking the freon levels and if that is okay then check the pressure switches and the wire harness to the clutch....
low on freon
the clutch engages a compressor that goes on and off to keep a particular setting.for example if there is not enough freon in the ac the clucth will keep running and clicking on and off
with just this info it's possible your a/c clutch bearings are going bad with just this info it's possible your a/c clutch bearings are going bad
The clutch bearing for an AC compressor is located in the center of the clutch. If the bearing goes bad, then the clutch is replaced as a whole part rather than changing the bearing.
your a/c compresore is bad
With the ac off your clutch the outer non belt driven part will not be turning. When it is turned on it will start to spin.
There may be some drag on the AC clutch when it is disengaged as the clutch 'free-wheels' during this time. When you engage the AC ,the clutch 'locks up' and the noise disappears. If the noise gets worse you may need to replace the clutch, if it stays the same and it not very loud, I would not replace it.
no it does't disturb the freon . the clutch comes off with puller and the coil comes off with a little lube and pry bars slowly. .
The AC clutch on a ford FS-10 is mounted on the front of the compressor. The clutch is removed by using a puller after the clutch nut is taken off. Mount the puller, and turn the center bolt. This will pull the clutch off of the compressor shaft.
The computer turns the AC clutch off when accelerating for maximum engine power. The AC compressor uses up some engine horse power.
AC Compressor clutch relay may be stuck. Remove the relay and see if the clutch releases.
The A/C clutch hub is rubbing on your A/C pulley and the gap needs to be readjusted. When the A/C is off the hub free wheels with in the pulley. When the clutch energizes the hub and pulley spin together and eliminates the noise.