2001 s3 air con problem

[plumbershands]

i have had gas checked and is ok when i turn on ac internal fan blows ambient air looked at compressor pulley spinning but seems as though the clutch thingy on end of compressor is not turning think it is supposed to ? any idea what to check next air con fuse ok is there any relay to check ? also saw another fuse saying magnetic clutch also ok have heard there is sensors but dont know where or how to check if i plug into a mechanics diagnostic machine is it likely to show up any fault as im low on funds due to cancer and need a cheap fix any help will be great help cheers mark

[kenney]

If you get someone to turn the AC on and off while you observe and listen to the magnetic clutch,you should hear it clicking,if it doesn't function,there is possibily a fault with the pressure sensor,or the magnetic clutch,a fault code read will show a faulty sensor