Aircon stopped working

[fuvureju]

I recently had my aircon checked for leaks and recharged.

The other day I was driving with th aircon on in the evening and suddenly it stopped demisting.
I later identified the f21 for the aircon had gone...but that has not enabled the aircon to actually work again.
it seems to work and a fan turns on when i turn the ignition to on (preheat the glow plugs) but the aircin does not actually work (ie no aircon)
However, the blower fan does work..

any ideas what may have gone wrong

Thanks

[fuvureju]

I forgot to say

the car is 1.9td D8 1996 with manual aircon

[mjb]

Bit late, but it could be the compressor clutch solenoid or a problem with the wiring to it