I have a Chrysler Grand Voyager 2.5 diesel 2002. It was standing for about three months and will need some work doing to it for the MOT, but once a week I started it and let it run and turned on the air conditioning just to make sure everything works, but now it's stopped. I turn the air conditioning on and the light powers up, but there's no compressor. I have checked the fuses and the relays, and swapped the relays about. The relays work but still no air conditioning. Any advice?