Air conditioning compressor not getting elec.

[jiggityjoe87]

I'm working on getting the a/c in my 94' 2500 working. when I hit the a/c button on the dash the climate control shows "a/c" but the compressor doesn't engage I have checked all the connections coming off the compressor and none of them are getting voltage when I push the a/c button. I have poured over my haynes manual and have not found any difinitive a/c wiring diagram does anybody have any recomendations what my next step should be. Keep in mind that this truck has 250,000 miles sooooo if there are any tests that I should be doing please let me know.