I have a cherry 1999 1500 custom van with 37k miles. It has the 5.7 liter engine. The rear ac is the aftermarket put in by the conversion company. The rotating **** on the dash controls the fan just fine. However, it just blows ambient air. No heat or cool. Is there a valve somewhere that could be causing this. Heat and air in the front work as advertised.

UPDATE: Found a .pdf file of the user's manual for the aftermarket rear air-conditioning and heating system. Found out that for heat to go to the rear unit the switch on the dash must be on "FLOOR". I had been trying to push heat to the rear using the "VENT" position. Changed to the correct position and now have glorious amounts of heat in the rear. Also operated the rear air conditioning and can feel the line going to the real cooling and the compressor kicks in. I think I may have more A/C after I charge the system a bit.