No airflow to defrost vent?

MARK I

MEMBER
2015 CHEVROLET MALIBU
2.5L
4 CYL
2WD
AUTOMATIC
120,000 MILES

HVAC system will blow proper temperature air, and will direct it to floor or face vents, however when I select defrost, air only flows out the face vents. Very minimal airflow comes out of the defrost vent.

Wednesday, November 9th, 2022 AT 3:59 PM

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Does the defroster indicator turn on when you select defroster? Also, do you have automatic climate control or manual climate control?

I'm looking through the wiring schematics and see one mode door actuator that controls all positions. It's for the manual system. If that is correct, the actuator may be failing or there could be an issue with the controller.

By any chance, do you ever notice a clicking sound from under the dash under any selection?

Let me know.

Joe

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Wednesday, November 9th, 2022 AT 7:45 PM

MARK I

MEMBER
3 POSTS

Hey Joe,

Yes, the indicator light does turn on when you select defrost. The car has manual climate control (1 knob for fan speed, 1 knob for temperature).
There is no clicking noise from under the dash. It’s a pretty quiet operation.
The actuator is working - I have looked up under the dash and watched it turn. I have not had a diagnostic check to verify if it is turning to the proper positions, but I’m thinking that the actuator is fine since it moves both directions repeatedly on command.

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Wednesday, November 9th, 2022 AT 7:56 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Disconnect the actuator and move the mode door manually to see if you can get full airflow from the defroster vents. Pay attention if there is any resistance when you turn it in the defrost direction.

Let me know what you find.

Joe

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Wednesday, November 9th, 2022 AT 9:03 PM