On my wife's 2003 Toyota Corolla/Matrix XR the A/C suddenly stopped working for no reason. She just pressed the A/C button and no cold air.
After checking into the problem I found that after turning on the A/C the engine RPM would increase as if the compressor was turning on, and the cooling fan would start to run as well. I had found that there were a few reasons for the A/C compressor not to turn on and the first reason was a lack of refrigerant in the A/C system. I checked the refrigerant and it was up to the correct pressure.
I had to run a jumper wire to the compressor clutch directly from the battery to get the compressor to turn on to test the refrigerant pressure and it turned on like it should have so that eliminated the compressor clutch as being the problem. My problem was that there was no continuity from the A/C switch inside the car to the compressor clutch.
After going to the Toyota dealership and asking both parts and mechanics I found out that the 2003 Matrix and Corolla had a potentially defective relay in the A/C circuit, in fact Toyota issued a service bulletin about the problem, not a re-call just a bulletin.
The defective A/C relay is called the M/G CLT relay and it is located in the fuse box under the hood next to the battery. The relay is solid state so you can't take the cover off and check the contacts all you can do is replace it.
The large contacts on the relay are the ones that are connected to the contacts, and the smaller contacts are the power contacts for the relay itself.
A new relay is around $70.00 from the Toyota dealer, an after market relay isn't much cheaper so it would be a good idea to get the dealer relay for the better quality part.
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