I exactly was facing the same problem and many of the ac repair centers rejected my case. Finally ac repair austin , a repair center at my place suggested me to get my ac out from a very professional auto mechanic and then leave the rest to the repair center. A complicated process through, but I got my job done.
CW= CASH WANTED,,, NOT WORK, they look for the easy jobs that they can charge an over inflated price for.. stay away from them. As GaryB said, take it to the mfg chassis dealer,,Chevy-Ford-Cat- Detroit, which ever type you have and let them repair it.