vt/x air con compressor clutch

[dagsy]

had the air con regassed & all goes well...when it wants to!! for some reason it only engages sometimes , like when you whack it with a rubber mallet.
i was thinking maybe the clutch is a bit dirty. how do you get it off, it takes a 13mm socket but i assume you need a special tool to stop it from turning.
anyone done this?

 

[NeddyBear]

Replace the whole unit man; there cheap and not worth having a hot car. $360.00