Defroster clicking noise when changing to vent mode

Possibly an actuator in your HVAC system. There are actuators to move the blend door, mode door, recirc door, and possibly others depending on your HVAC options (climate control, dual control, etc). With your car running, can you change the temperature from cold to hot and back, and can you direct airflow to floor, defrost, and dash vents? When you select recirculate (max a/c), can you hear the change? If you have problems with any of these, you may need to replace an actuator or one of the doors may be jammed.

Mode door or temp. door actuator, plastic gear is worn out . Can you change air flow , defroster , vents , floor direction etc... ? Change heat to A/C etc.. ?

HI THE CLICKING SOUND IS PROBABLY A HEATER/AC ACTUATOR WITH A STRIPPED GEAR , WHEN THIS HAPPENS TRY TO MOVE THE HEATER CONTROL KNOB FOR THE MODES (DEFROST/FLOOR/VENTS) SEE IF NOISE CHANGES . IF IT DOSE THEN THE ISSUE IS WITH A ACTUATOR UNDER THE DASH

Got kids? Years ago, mine loaded the defroster ducts with toys, candy, etc.
Otherwise, please create another post and identify the year, make and model vehicle you're talking about before posting your question.

Mode Door Replacement

Removal Procedure

1. Remove the I/P carrier. Refer to Instrument Panel (I/P) Carrier Replacement in Instrument Panel, Gages and Console.
2. Remove the screws from the mode actuator.
3. Remove the mode actuator.


Click to Enlarge

4. Remove screws in order to separate the defroster/mode outlet cover (2) from the HVAC module assembly (1).


Click to Enlarge

5. Remove the mode door (1) from the heater module.

Maybe the actuator needs to be replaced?

The mode door defaults to defrost when it loses vacuum. I would start by checking for cracked/ loose vacuum hoses in the engine compartment.

Do you hear a clicking noise when you turn your truck on? Its probably the actuator. While the defroster was on I removed the fuse locted under the rear driver side seat. I think its 36B. It stopped the clicking noise and my air vents work well now.

The mode door actuator is bad .
2000 Cadillac Deville mode door actuator replacement

It sounds like the air distribution door motor is bad. If you turn the fan speed to low with the ignition on/engine off and try to change the mode to something other than defrost, you should faintly hear a motor running. If its making clicking noises, then it is most likely stripped. This is a fairly common problem with mode door motors. It will have one on each temp door for the dual climate control as well. Those ones usually last longer.

It may be the mode actuator. Have you heard any clicking or other strange noise ? Under the drivers rear seat, in a plastic box is a fuse panel. Remove the two retainers, and the cover. Remove the HVAC or A/C fuse for a minute or two. Reinstall the fuse and this will make the A/C system relearn. Whwn you put the fuses back do not touch the A/C controls. Start the truck and leave it run for two or three minutes. Then try to change the vent from floor to vent and defrost. If this does not work you will need a mode motor. Good Luck