hi i have a c5 2002 2.0 hdi with manual temperature control with aircon. the aircon gives a high pitched whine when its going to work then about 30secs later starts blowing cold air for a few minutes then starts blowing warm air. it has got plenty of gas in the system i have checked it with a pressure gauge when the system has been on a long while about 1 hour the pressure reeds very high about double what it should be when cold pressure reeds ok. anyone got any ideas to help me?? many thanks mark