When I switch to Max a/c on my 2003 model the interior fan supply door (wherever it is) does not seem to open. In other words, back when it worked I could hear the loud sound of air going to the blower from the cabin, now when I switch to Max a/c there is no loud air sound.

I checked the vacuum hoses on the small vacuum canister under the glove box/passenger side dash. The hoses are intact as is the canister and when disconnected I can feel a strong vacuum being pulled on the hose connection.

Therefore I suspect either a switch/electrical issue or some type of mechanical binding of the vent door but really I have no idea????

Any suggestions as to how to troubleshoot?

Greatly appreciated,
Bernie