Volvo Repair: 740 Climate Control Issue, compressor system, relay switch

Question
I have no power coming to the compressor, system is full.  Relay?  Switch? Checked fuses and fan is operational.

Answer
Hello Richard,  There a few "hoops" the current needs to jump to get where we need it.First is the a/c switch panel. ECC or MCC ? either way there is a chance that inside the control panel a solder point for power out to the compressor may be "bad" loose.The only known way to find out is to remove it and squeeze it,gently like a sandwich,with your fingers on top.yes thats right.What your accompishing is to flex the circuit board just enough to make contact.With the unit plugged in you will hear the comp. kick in.Now when the current leaves there,its on to the "low pressure switch" One of the green wire will have current (if the control panel is working),when pressure of at least 3rd of a lbs. the switch send current to the comp. Now if its still not kicking in,check to see if the groung wire,that is attached to the adjusting bracket,is in fact connected.On the outside chance that all the above is well,and its still not in the mood,with the engine Off and the key On,gently move the wire that goes to the clutcha bit ,in and out,slightly,if the clutch engages then it time for a replacement unit.thak you and good hunting