Where are 2006 Volvo S40 AC high and low pressure valves?

The low pressure port of the A/C system usually has a blue or black dust cap and is located either on the larger diameter metal tubing typically found between the evaporator and compressor, on the compressor itself, or on the receiver drier (orifice tube systems only). The high pressure service port is found either on the smaller diameter tubing or the compressor and is larger in diameter. Only charge through the low pressure port. There is a web site with a lot of help full information about your auto a/c system and will give you a pinpoint locations of both your high and low side port check the link below.