My Granite (MP8) truck just recently went to the dealership to have a Box Sensor replaced. When I got it back the air conditioning is not working. I noticed that the engine fan stays on full-time no matter what. coolant level is okay, doesn't run hot, power to AC compressor, AC compressor has good 3.7 ohm resistance on the clutch, refrigerant charge is good. Beating my freaking head against the wall troubleshooting this thing. everything seems to work as it should however, the high and low side of the AC system is not getting cold or warm. blower motor in cab is fine, clean cabin filter and heat exchanger. everything appears to be doing what it's supposed to do however there is no chill occurring on the coolant line. Just stumbled across a couple posts mentioning how the engine fan is associated somehow with the HVAC system. Also someone mentioned something about a DPF system sensor being bad on their truck causing the engine fan to run indefinitely. Caused me to speculate if them changing out my sensor is causing my fan to stay running and in turn causing my AC not to function properly? Any help would be greatly appreciated.