1983 242 whistle when floor air button is depressed.

Hello, I have a 1983 242 DL. When the floor air divert button is selected, their is a horrible whistle that comes from under the dash somewhere. Would this be in the three button switch on the dash, the air flappers that compress or? Thanks for any ideas.

It could be a leak in the selector switches. One of the rubber bellows on the vacuum actuators for the floor may have a small slit causing the whistle. If it is that loud you can probably follow the sound to the leak.

^the thing that looks like 4 beans in a pod