Aircon Stopped Working Mondeo Mk4

[makepeace1]

My Aircon has stopped working

I have had it checked and it was reading 0.520kg which is correct

I have checked the relay and the fuse and they work it just when i press the button in the car on the climate control it lights up and says a/c but the relay doesn't click to engage the compressor if i cross the pins that the relay does the compressor starts working and the car gets cold

but unless i cross them pins it doesn't get cold as there is no power to the relay to engage it

It was working up till yesterday morning i went to the shops it was working i got in the car to come home and since then it has not worked

has anyone any ideas ?

TIA

James