I am trying to get my air-conditioning working

Firstly, the car has a problem in that the hot/cold control dial on the left hand side, is not functioning fully. The control dial will only rotate from cold, at say 1 o,clock around clockwise to about 7 o,clock.

Secondly, the reason I have mentioned this in the first paragraph, is that I am unsure whether the heater control dials have any sort of micro switches, that may be fitted behind the heater controls panel, with regards as to why the air-con is not working.
Today, I have looked at pulley on the compressor pump and whilst the belt and the inside part of the pulley are moving satisfactorly when the engine is running, but the outside part of the pulley is not rotating.
Inside the car, the fan blower speed control dial is working at all speeds and the air direction control is working correctly and the air recirculation switch is working correctly too. However when you switch on the air-con switch nothing happpens, no click as the clutch should be engaging.
Another thing I was aslo wondering is if at all I can drain and refill the system myself, with one these modern day diy kits that seem to be available these days

The car is a 93 1.6cc 8v BX TXi automatic.
Any help or advice would be gratefully received and many-thanks
Vince,