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.

1 answer
Go to this site http://www.parts.com/ 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.