I know nothing about it. The AC in the Celica is broke and has been. This about the last area of automotive home repair that I haven't dabbled in. Here are the issues:

-spent about $600 at the dealership a few years ago getting it fixed. It worked for the rest of that summer, but quit again the next spring.

-AC light on HVAC controls comes on when you push it

-Compressor does not click on. You look at the center of the compressor pulley and it does not kick in when you turn on the AC.

Odds are I probably have a leak somewhere. Can I find the leak myself? Or do I take it somewhere?

Is that all there is to AC system repair? Finding leaks and fixing them? How do you troubleshoot individual components?

they usually put a dye in the refrigerant and then they will be able to find the leak with a blacklight. They usually have to fill the refrigerant and dye, then have you come back a week or two later so they can find the leak and fix it.

You are right about the lack of refrigerant: the compressor will not turn on because there is not enough pressure to open the valve (or something like that).

There should be a high and low pressure switch. You might be able to "short" the switch out and get the compressor to kick on. I did this on a friend's CRX when we were trying to figure his AC problems out. Did you get the system changed to R134A? If so, go buy a can of coolant at WalMart with the leak dye in it.

I have NO CLUE what was replaced, nor if it was converted. I need to call them up and have them pull the records on the service done.