Update on EATC problem / Vents closing

[Mark W]

I replaced the head unit as the poster at the end of the other post (and my mechanic) mentioned. That wasn't the problem. It turns out that the vacuum motor that controls the vent output attaches to a small plastic arm that opens and closes a flapper valve. That plastic arm has two little nibs that stick out from it that clip into a hole in the arm off the vacuum motor.

Can anyone answer: What is holding the plastic arm onto the flapper valve shaft? Is it bonded, screwed, or just slipped onto the shaft? How tough would this be to repair without tearing out the dash? I tried drilling it and putting a piece of wire in it, but you'd be surprised how hard that is (a twist tie would work, but for how long?).

Thanks