Factory A/C air shut-off valve ??

[Luis_gz06]

I just installed a used air shut-off valve (Flapper) the one that goes underneath the cowl panel on the passenger side. I know these are suppose to control the outside air flow into the cab but it doesn't flap all the way!! When I pressed the vacuum actuator, it wont shut all the way. And the shut-off valve is not tight all the way with the plastic nut the goes inside. It is lose a little and when it flaps, it falls down. What can I do???

Here are some pics to see what im talking about.