I have a 2013 express 3500. The ambient temp sensor doesn't work most of the time. Whenever it's not working properly the engine fan seems to be running all the time. As soon as the sensor works the van gets significantly quieter. The water temp always settles at 210 degrees when the engine warms up.
Is it possible that the ambient temp sensor is actually effecting the fan? I haven't been able to figure out exactly where the sensor is at.

 

it's located behind the grill, down low. Check the wiring and connector

 

My 2015 3500 has a mechanical fan clutch with no wires going to it. It could make the fan loud only by increasing the idle RPM.