Once again I also have the "Service Ac System" and "Ac compressor off" message I have had mechanics check everything and nothing seems to work. One mechanic offered to connect the compressor directly so that every time the car is turned on the ac will turn on but that was not something i wanted to do. From that i know that the problem is that there is no power going to the compressor and assume it is a pressure swtich or relay but, which one. Any help will be greatly appreciated. Please forgive my wordage I am not mechanically inclined but, 104 degree weather makes you try anything. Oh I almost forgot its a 97 deville. Also a Message to "service air bag" once in awhile aND "check oil level" and "Change oil" And everything is fine with these things. Thanks

 

Need to know what code is set when the a/c quits working.
Ask the mechanic what the code is and tell us what has been replaced/repaired so far.
From what you just wrote,I would also look for a new mechanic.