I just purchased a 2005 (Built 4/04) Scion xB. The A/C doesn't blow cold. The light comes on on the dash when pressed. I appear to have power at the plug on the compressor (my multimeter died today, hence appears. Using the old test light) but the clutch doesn't engage. On the car side of the compressor plug there are two wires, one black with a white stripe and one blue with a black stripe. According to my wiring diagram, the blk/wht goes directly to 12v hot via a/c 2 fuse 7.5 amp. The fuse it good. The power is good. The blu/blk wire goes to the engine control module (ECM). I presume the wire going to the ECM is a switched ground wire? On the compressor side of the plug, there are 2 wires. One is black, one is red. I have grounded one side and 12v the opposite, I have done the same reversed, and I have applied 12v to both prongs and the clutch magnet still doesn't engage. Here are my questions....

1. Does the ECM in fact use a ground to switch on the compressor?
2. Are my original test procedure correct, ground one side of the compressor plug and 12v the other prong?
3. Do they sell just a clutch for the compressor, or do I have to replace the complete compressor?
4. Is this a common part to fail on these?

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You put 12 volts on the clutch and you know for certain that its not engaging? put an ohm meter on the leads.... resistance should be low. find the repair manual on this site and it will tell you what the resistance spec is. if it is high resistance or infinity, then the coil is open and you need to replace.
I just had the compressor replaced on my 06 xA. 06 went with a magnetic valve design instead of the magnetic clutch that you have. the coil partially open and the valve wouldn't energize which didn't let the compressor compress. also, you might also have an A/C amplifier too. you'll have to pull the dash to get to it.

but first verify that your compressor is good before you pull the dash off. all the repair manuals and wiring diagrams are on this site as a resource. use them if you prefer not wasting your time and chasing your tail all day long. My compressor was replaced under my extended warranty which cost $2500!!!!
Know your $hit before you get ripped by the dealer.

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