[Mark911C2]

Turned the cabin temperature control knob up the other day to a higher setting and the heat came on but would not adjust back to a colder setting when I moved the temperature control back to the coldest position. Is there a sensor inside the cockpit that gives feedback to the temperature controller? I noticed a plastic circular insert next to the cigarette lighter (just to the right of it) that has plastic slats, some of which are now missing (broken off). Can't find anything that describes that insert so don't know if that's part of problem or not. Appreciate any thoughts on this!