i have a hissing dash

it seems to come from the switch area, but i can also hear it back by the recirc door, kinda hard to hear exactly where it is coming from.

when i push the button in (sucking vacuum) it moves the door part way but continues to hiss.

if i reach down there and close the door, it stops hissing and works fine until i shut the car off and then it will keep for a bit before it lets go.

how long should it stay shut with the car off to consider it 'not leaking' ?

when i leave the door closed (recirc on, button pushed) i get a good leak of cold air on the floor from that area. when in keep the door open (recirc off, button out, no hiss) no cold air either? this seems totally backwards to me, but maybe i don't really understand the system then.

the fact that i can close the door by hand and the hissing stops makes me think it's the switch more than the actuator, but i'm not really sure because maybe i don't understand the system (although it shouldn't be difficult)

i also know i can put a tennis ball down there and that will fix the issue until i care to have the door on recirc.

thanks
michael