Need help with AC troubleshooting

[John Michael]

Hello. I need some help. If the AC/Heater won’t switch out of defrost mode, what could it be? It’s stuck blowing air on the windshield despite turning the dial any which way.
Thanks for any help.

 

[Burbonsurgeon]

Check all your heater box servo motors. If you can feel the motor activate but the flap doesn't move most likely the plastic final drive gear in the servo gear box has spun in the output shaft. The plastic gets old and brittle. Once that happens you just have to bite the bullet and install a replacement.

 

[John Michael]

@Burbonsurgeon Okay, thank you. I’ll look into it!

 

[east302]

It should look like this, sometimes the linkages can come apart. Otherwise, the internal gears can crack as mentioned above. The silver dial on the actuator may then not turn smoothly, only partially rotate or may make a ratcheting sound. It should rotate between the raised lines on the actuator between floor to defrost.

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[John Michael]

@east302 Thanks for the info! I’ll reference back to your photos when I go to take a look.