[busboy4]

Hi
I think you may have a vacuum or actuator problem. The rear system is slave to the selection on the front panel. I assume your front A/C operations are normal? The flow of air to top or bottom and/or through the heater core/ A/C condenser on the rear unit is dependent on the front selection. There is a vacuum actuator that opens/closes the heater core door on the rear. If the air is directed through the heater core it comes out the bottom, if through the A/C condenser it goes to the top. The actuator is mounted on the side of the rear fan unit and based on the diagram looks like a canister with vacuum lines running in and out. Of course this is all behind the rear trim. So, if you can get at it, I would check the security of the vacuum lines in and out of the actuator, listen for leaks etc and check that the linkage from the actuator to the heater door is intact.

Hope that gets you somewhere. Let us know.