2012 Chevrolet Express, I have 2 HVAC controls one for the front of the van, 1 for the rear. The rear is not blowing anything.

SOURCE: rear air a/c

Probably plugged or failed expansion valve on rear evaporator. Both front and rear are plumbed in parallel so if the front is cold, a problem with refrigerant flow at back unit almost has to be in the expansion valve.

SOURCE: engine 1 fuse keeps blowing when you turn the key

Engine 1 fuse powers the computer and some sensors. I had this same problem on a 98 chevy van 3500 and found the wire going to one of the oxygen sensors had shorted out on the heat shield. Inspect the wires going to all of the oxygen sensors. On this van one of the oxygen sensors on the driverside the wire was laying on the heat shield which eventually rubbed through the wire and shorted it out blowing the fuse. Your short could be on a different sensor but check all of the oxygen sensors because the wire runs so close to the sharp heat shield.

SOURCE: 2006 Chevrolet Uplander LT 2wd bad road noise in the rear end

i had the same problem, i found out that both rear torque arm bushing are filled with liquid grease, when they go bad all the grease comes out of them and then the metal sleeve inside the bushing starts the hit the bolts, when you hit a bump. that was the loud noise, that i had.

SOURCE: I need the serpentine belt diagram for a chevy Express Van

DRIVE BELT DECAL SHOULD BE UNDER THE HOOD.OR YOU CAN GO TO DEALERSHIP GET ONE AUTO ZONE OR ADVANCE AUTO PARTS CAN GET YOU ONE.OR YOU CAN BUY A HAYNES REPAIR MANUAL IT HAS BELT DIAGRAM.

SOURCE: 2005 GMC Yukon Denali XL - Climate Control issue-

Are you aware of any codes that may stored in the body control module and do you hear a clicking or ticking noise in the rear?