Having problems with your 2005 GMC Sierra 2500HD 4WD ?
My 05 sierra 2500 6.6l won't divert the airflow through the front vents or floor vents. It just stays on defrost even when I change the controls. Is there a fuse or relay that I can check?
Check for a loose vacuum line behind the glove box.
Repair Help & Product Troubleshooting for 2005 GMC Sierra 2500HD 4WD
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