Ok. I was pretty convinced that I would be pulling the dash to replace my pods because I was getting a rythmic tap, tap, tap, noise from the center vent in cooling mode. Another poster had the same problem and it was a small leak in the centre vent diaphragm causing the flap to open then close partly and then open again thereby making that rythmic taping.

Now with our cool sunny fall weather the center vent is operating normaly. I get cool air from the center vent and there is no noise. The only thing I see as being different is that the outside air temperature is cold enough that the ac is no longer needed for cooling, instead it is using direct fresh air.

Does anyone know if there is a difference in how the vent dampers are positioned between cooling with AC on and cooling with AC off or cooling with high outside temperatures and cooling with low outside temperatures (free cooling)?

Thanks.

I can't answer your specific question, but I CAN tell you how to easily check the pods:

Remove the glovebox liner and use an auxiliary vacuum source on each line that connects to the switchover valve to the lower left of the glovebox. If you find one that won't hold a vacuum, there's your culprit.