Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
From what you are describing here, it sounds like the problem may lie in the Mode Actuator or the internal door of the HVAC Housing. The Actuator is located behind the center/driver's side of the dash. To gain access, remove the driver's side knee bolster and lower insulator panel. Carefully inspect the linkage to the actuator and make sure it is in tact and not binding and is making its full scope of travel. Inspect the vacuum line for any cracks, holes or loose connections. Make sure to inspect the vacuum line all the way to the vacuum reservoir located under the hood in the driver's side rear corner. If the visual inspections check ok, remove the actuator and turn the door by hand. The air flow should now be correct. If not, the problem lies internal of the HVAC housing. The housing will need to be removed, opened and repaired as needed. If the air flow is correct, make sure enough vacuum is getting to the actuator. If the vacuum is ok, replace the actuator. Please remember to leave a rating using the rating system at the top of this page or accept the answer so I may be credited for this Q&A. You can ask follow-up questions any time, even after you rate or accept.