Anyone knows an easy way to test if the recirculation flap closes on a 126?

I have a feeling that mine stopped working.



For those of you unfamiliar with this system the recirculation flap is supposed to close 80% in the "O" and the A/C buttons (all 3 buttons from the left) but is supposed to be open only in the EC position.

Anyway here are my symptoms:

How it used to work: switching from EC to O: I can hear a slight thump and I get no ram air.

How it works now: switching from EC to O: No thump and I get ram air (which is not supposed to happen)

The reason why I want to check this flap is because it will impact the performance and reliability of my A/C system in the coming summer months