RE: 2000 b1500 rear ac
Speaking from experience with 1999...
I don't think it's related. As you may know, the rear shares the flow of refrigerant with the front, with one compressor for both. However, the rear has its own evaporator core and thermal expansion valve.
Also, the radiator coolant flows through the same AC evaporator in the back, I think vacuum controls the flow -- on my '99 2500 van it's either full on or full off-- you can't mix them to control temp in the back like you can the front.
Maybe something got messed up and your getting hot coolant flowing through it? Or maybe the expansion valve. I am not sure how to diagnose the rear expansion valve being bad, but maybe you could check the temperature of the lines from below the floor -- feel the AC liquid line (the small one)-it should be hot vs. the AC suction line (the big one) - it should be cold. And the two coolant lines should both be cool because they are not supposed to be flowing unless the heater is on.
Also -- take the cover off the blower and be sure there's no air blockage and be sure it all cleaned out. There's a filter that picks up dust and dirt.
Hope this helps,