Front AC Problem / Rear AC OK

[Montana Junk]

I have a 1998 Pontiac Trans Sport with 207,000 km and dual front and rear AC. The front AC pumps out unconditioned air but the rear AC pumps out cold air. The front AC light still goes on but non conditioned air comes out of the front vents and cool air comes out the rear AC vents. The heating system on the other hand works fine for both the front and rear although the blower motor resistor needs to be replaced because fan speeds 1 and 2 don't work.

Are the front and rear AC systems connected? Do the two systems have common parts? Are the refrigerant loops seperate? Do you think it may be a damper problem at the front of the vehicle? Would the blower motor resistor affect the AC? Can anyone offer any insight?

[LMP]

Unless other details emerge from you, here are my 2 cents. Notice I do not have detailed documentation on the '98 and no "historical knowledge" of that model year but the overall design uses rules that do apply all across the board:
FIrst I understand that you DO have FULL A/C both front and back, then with front and read evaporators and the refrigerant linres that go to the rear unit. My replies are based on that assumption:
- there is one A/C compressor only and if you do have refrigerated air in the back, then the front can also be supplied with refrigerant. There are no controlled valves on the A/C refrigerant lines. THe only "valve" is the expansion tubes or orifices that releases the high pressure refrigerant to the low pressure evaporators and in theory, some contaminant might have clogged this line in the front but I never heard of that.
- since you say you have heat in the front with what I understand as normal air flow , then may be you have a problem with the mixer/diverter door: this one (its electric motor actuator) could be damaged in a way that has the air, although cooled, continue passing through the heater core: this happens often. (air always passes through the evaporator first, then is fed through the heater core or diverted around the heater core.

[fixitG]

Did you end up fixing this problem? I have the same symptons with
a 1998 Transport (only 80K miles)