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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22769
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 2008 c4 grand picasso and my a/c doesn't work. My

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I have a 2008 c4 grand picasso and my a/c doesn't work. My a/c clutch on the compressor doesn't appear to engage. Would this be a relay problem? If so is the relay the green relay in the front of the fuse box under the bonnet?


the AC won't run if the gas pressure is low so 1st thing to check is the gas pressure also check that the AC rad / condenser is clear of any debris and there's nothing in front of the air flow to it, next ensure that the AC pump drive belt isn't slipping and if any doubt replace it.

Also check that if there's a pollen filter to the cabin air inlet that this is clean and free flowing
Next you can test components simply by checking the temperatures by touching them with the system running. with the engine at operating temperature and the AC turned on it should be as follows:
A hot compressor / pump
A hot high pressure refrigerant line from the compressor to the condenser
A hot condenser on the inlet
A warm condenser on the outlet
A warm liquid line from the condenser to the evaporator (before the expansion valve or orifice tube)
A cold evaporator outlet line
A cold low pressure refrigerant line to the compressor

If you get a different result from the above then suspect a blockage in the line or the component whose temperature is abnormal, this can be confirmed with a pressure test

Then if you're happy the temperature control is OK ( does it do hot as well as cold?) I'd take the car to an garage that can read the pressure levels of the system so the level of gas can be checked hopefully all it needs is a re-gas

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