[mmagliaro]

The compressor occasionally cycles off and on, and you will hear a click when it does this. If it's doing it a LOT, and that's what the clicking is that you hear, it COULD be this switch, but it could also be low on refrigerant. You should take it to a service garage (if you can't do this yourself) and have them check that the refigerant is full and that there are no leaks. They can inject an ultraviolet-sensitive dye into the system, and then shine a blacklight on it to look for leaks.

You can get a simple to use kit at auto parts stores that comes with a gauge and a can of refrigerant-and-oil-in-a-can. It will have instructions telling you where to screw the gauge on and how to read it. If it's low on refrig, you can add some with the kit. If that fixes it for a while, but the problem comes back in a week or two, you definitely have a leak, and you need to get it fixed.

If the system is full, and the compressor still doesn't run (and you get warm air), then you can think about the switch. The switch is on the passenger side of the engine compartment, near the firewall , screwed into the side, near the top, of a large silver metal vertical canister (I think this is the drier/accumulator). It looks like a small plastic cylinder with
a 2-wire connection on the end of it. The 2-wire connector pulls off, and the switch itself just unscrews from a connector. Just as you pull it off, you'll hear a quick "sssssst" of gas escape, but no more. The switch is screwed on to a schrader valve that will close when you remove it, so you won't lose refrigerant.

I determined that mine was at fault because I KNEW the system was full, and it would go warm for many minutes, so I was able to rap on the switch with the rubber handle of a screwdriver, hear the compressor click on, and STAY on, and that pretty much convinced me the switch was hosed.