Rover 75 air conditioning doesn't switch on

[Alexander MOB]

Hi All,

I have a Rover 75 Club diesel with a problem that I try to fix. I have to go on a road trip and the air conditioning is not working, the car transforms in a sauna and I have to drive with the windows down. It's horrible
;
First I went to fill the installation with gas but hasn't get any better. The guy from this service wasn't doing electronics but he knew a few things and was nice enough to guide me. So this is what I did:

- took the air con relay and checked it with a digital multi-meter
- I put 12v on the relay coil, it clicks very good and the contacts work perfect (checked the switch on/off with the multimeter's buzzer)
- went to the car and with the relay dismounted and the AC on I check the pins from the car side
- the coil pins don't have any signal but the contact/switch pins have 12 volts (for the compressor)
- I take a piece of wire and connect the switch pins. They make a small spark and I hear the compressor starting.

I live it like this for 10 minutes but the air still doesn't get cold... probably now I have to refill it (the guy said that if the compressor doesn't work he cannot refill it because he needs some pressure)

So the relay coil doesn't receive the signal to start the compressor?

What should the issue be now? On the air con pipes there is a temperature sensor with a switch that this guy said it could be broken. Is there a way to check it before buy it?

It could be something else? What do you guys think?

Cheers and regards,
Alexander