Problem with switching from heat to a/c on 1997 Ford Escort

What do you call the thing that looks like a gear that changes from heat to A/C? Heater and A/C both work fine but the "gear part" is broken so has to be changed manually.

Asked by for the 1997 Ford Escort
Go to this site put in your year, make and model and put vacuum motor in the search box, here you'll see view image click on that and you'll see a complete diagram of your heater and be able to locate the part your looking for.