We already put in a new expansion valve from the dealer. Still same problem as prior to replacing it. Rec/dryer has not been touched yet, but didn't think that would change anything. We did blow through the evap when the valve was out and no restrictions.

Thank you for the reply! We will go after the rec/dryer next. We tested the evaporator with dry nitrogen, as we always use for testing. The system wasn't empty when we received the truck. We did evacuate it properly- prior to re-charging, after replacing the valve. In addition, when the system is running- you can hear a hissing sound at the evaporator, that I haven't noticed on others... But like I said before, it's like the system is running backwards. The condensor is working, one line warm the other cooler, the larger suction line at the compressor does not get cold or even cool. The evap in this truck has a series of small copper lines on the high side and one large on low side, those little lines are getting cold and large line is warm... Does this still sound like rec/dryer or restricted/plugged system somewhere?? We've done a/c work for many years and never seen anything like this one. I've even called techs over from other local shops to get their opinion- and we're all stumped. Customer is getting impatient... (Me too!) Truck model is a 8100 and has a cummins ISM engine. Thanks again!!