2004 Chevrolet Silverado climate controll vents

135,000 MILES • 6.2L • V8 • 4WD • AUTOMATIC
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DRUMMER49
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  • 1 POST
air only comes out the defroster vents when ac mode is selected. I understand it is the mode door how do you move the linkage
Jun 15, 2015 at 8:27 AM
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CARADIODOC
  • ✓Experienced Mechanic
  • 34,413 POSTS
Most likely your mode doors are operated by vacuum motors, and the vacuum hose is broken or disconnected. The system has spring-loaded doors to default to the defrost position for safety. Your feet might freeze but the windshield will be clear. There's a vacuum hose routing diagram on the emissions sticker under the hood. Look on that for the small, hard plastic hose going to the firewall and be sure that is not broken.
Jun 15, 2015 at 8:45 AM
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WRENCHTECH
  • ✓Experienced Mechanic
  • 20,760 POSTS
The mode door actuator in this truck is electric, not vacuum.

You can't really manually move anything while the motor is on there and you can't remove the motor and do it because the linkage operates about 3 door simultaneously. The one thing you may be able to do is help the motor along with your hands while moving the mode controls and then leave it in the position you want.. The actuator is on the end of the HVAC housing on the driver's side. You should be able to access it from under the driver's dash.
Jun 15, 2015 at 9:12 AM
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