I bypassed the relay and it works gets ice cold.Try to jump'r the high and low pressure swithes but no go.Swapped out the relay no go.Any thoughts and thanks in advance for any hope.Maybe the controls inside the cab??96 2500 4x4.

 

I had a 98 that did that, did not have the hot feed to the relay in the box. Instead of tearing the box apart I just bent the feed terminal up, pluged the relay back in the box and wired a new feed to the bent up terminal. Its been working ever since.