Defroster makes a clunking sound when selected

Welcome to 2CarPros.

The component you are referring to is a mode door actuator and this vehicle has one specific to the defroster. If you look at picture, number 4 shows the defroster actuator location. Here are the directions for replacement:

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FLOOR OR DEFROST MODE ACTUATOR
REMOVAL

Picture 2

1. Disconnect actuator from HVAC module wiring harness.
2. Remove actuator to HVAC case screws and remove actuator.

INSTALLATION
1. Align flats on actuator opening with flats on door shah and install actuator with screws.
2. Connect HVAC module wiring harness to actuator.

Torque:
Actuator to HVAC Case Screws: 1 N.M (9 in. Lbs.)

NOTE: Any time a HVAC module mode actuator or HVAC controller is replaced, the HVAC controller will need to be calibrated to insure proper air distribution.

3. Calibrate mode door by simultaneously pushing the A/C and RECIRC buttons on the HVAC controller 3 times each within 2 seconds of initial push.
A/C and RECIRC button LED's will flash while this calibration is taking place.
Calibration will take anywhere between 10 to 30 seconds depending on battery voltage.
LED's will quit flashing when completed.
4. Cycle ignition and verify major operation.

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Let me know if this helps.

Take care,
Joe

Welcome back:

The component is electric and not vacuum operated. Inside, there are plastic gears that can break or wear out. When that happens, you will hear the clicking noise.