2000 Cadillac Deville AC off

I had my valve gasket fixed. The ac was cranking cold when I brought in, when I got it back the ac said off on the dash. I brought it back the mechanic said it was the high pressure switch. I change it and still no ac. I also changed the ac swicth and nothing. I ran a wire from the compressor to a power source and the clucth engaged, just to make sure it worked. I dont know. Its hot in Florida, any suggestions.