I own a 2013 Ford F650 Rollback with 6.7 Cummins engine. The air conditioner has stopped working, Freon will only stay in it for a day. It has been to 2 shops, no one can find the leak. One shop put the dye in the lines and again could not find the leak(s). You would think if the freon is leaking out that fast someone would be able to find the leak(s). Any suggestions or thoughts????