If it doesnt have a back blower that would be the first one I have ever heard of. Are there two blower switches? Is it a conversion van?

 

Perhaps I am thinking of my old 86 Ford Club Wagon...I believe I was told it had two separate a/c units? This is a conversion (Glaval) and does have two blower switches-one on the upper left panel controls the back. Ford told me a few years back that the front and back were all on one unit.

 

They share the same Compressor and condenser, but have separate evaporator units and blower units. They have shared refrigerant lines that splice together. Glaval installs aftermarket rear AC on most of their units, which is usually installed all the way back in the rear of the vehicle on the driver side. You would find a plastic trim cover over the blower unit. Some use dual factory air units. The aftermarket units will use rubber hoses to the rear unit and the factory has metal lines all the way back..

 

So Homer,
How would I find a possible leak in the hose leading to the back vents?

 

It sounds to me that you still have the blower running with the AC off, which will naturally pull warmer air through, possibly through the heater section of the rear unit, which is also a rear heater. These after market units arent the complex and well design of a factory unit. It could be that the water valve to the heater has a vacuum leak allowing hot water to flow all the time, or when you turn off the AC the water valve is allowed to open because the AC is off. (IE vacuum is turned off to the valve) You will probably find an inline water valve in one of the hoses going to the rear heater under the vehicle or under the "doghouse" or in the engine compartment

 

Thank you Homer. I will check on it.
TomMc