AC flap (behind glovebox - Proper operation?

[ck42]

Just checking that flap behind the glovebox to ensure that it's closing all the way (AC doesn't seem _quite_ as cold as it should be (R12))

Anyway, it's working like this.

With the ACC button in the OFF position (Circle button), the flap is closed.

With the VENT button on, the flap closes.

With the AC on, the flap stays closed. With the AC on and in the MIN position, it stays closed.

Is this right? Does the flap being in the open position allow fresh air in? And...when the AC is in ON but not in the MIN position, shouldn't the flap be open slightly, or is this flap an 'all-or-nothing' flap?

On a side note, I was looking for the roof temp tube that supposedly runs down and behind the glove box (the one that rots). Didn't see anything that looked like it. Is it back there?