ok im having a weird issue with my 97 850 t5, when the defrost is on it only blows heat on drivers side, passenger side blows cold air?? also does it when you change the flow to the floor or panel vents.

 

There is a flapper door that opens and closes to allow heat from the radiator in the dash to flow into the car. I bet the door is not opening and blocking air from flowing through the passenger side of the heater core.

 

thanks I will check that this weekend