I've got this 5 cyl, turbo s80 and the air conditioning has begun to "act up" on me. Sometimes it cools, other times it blows warm air. I took it in to be recharged and the mechanic said I was a little low and it showed no leaks. My neighbor, who owned a auto shop for 30 years, seems to think it could be the pressure switch or the expansion valve. I've been looking all over the engine compartment and haven't been able to locate either. Any help identifying where these components might be and how to replace them would be greatly appreciated. TIA folks.