Bunk HVAC and fan have no power

[kmk]

Check your blower by applying power directly to it. If it works, check your fan knob, I had one that was loosing contact. If you have access to diamond logic check for codes, the rear unit has a "processing unit" that's mounted on top of it, if it loses communication with the bc it will shut off the controls in the back. Check its harness and connector for corrosion, open the black box and see if there is any moisture, corrosion related damage to it. The thing is not sealed. The Behr part number is P3728001/BHTC 5hb-965-200-02, they rarely go bad though, so focus on the basics.