Air Door Actuator on 2003 Chevrolet Trailblazer

Wher do I locate it and repair

Asked by for the 2003 Chevrolet Trailblazer
Which actuator air door, recirculate, temp, mode?
Defrost air all the time
You need the Mode Door actuator. On the drivers side of a/c heater box. Can be removed if you reach above the gas pedal. Experienced person only takes 15 minutes.