AC/ heat temp control not working on 2003 Kia Spectra

The temp control is not working. It always blows out hot air. Even when you turn on the AC, hot air blows through the vents. I can tell that the AC compressor is engaging. My question is...Is their a door or motor that controls temp? What's most likely the problem and how difficult is it to fix?

Asked by for the 2003 Kia Spectra
Sounds like blend door problem or actuator for the door. Could be vacuum or electrical operated. Partial dash disassembly is required for inspection and repair.