Having problems with your 2006 Chevrolet Silverado 2500HD 2WD ?
2005 Silverado 2500HD 4WD - It appears that the pneumatic valve controlling the directional air flow from my heater/AC is getting stuck. When I switch the fan to front window defrost then back to front/bottom no air flow comes out the front or bottom air vents - the flow is entirely out the upper defrost vents. If I drive over some bumps the valve loosens and air flow again comes out the front/bottom vents. How do I fix this??? Thanks
The default configuration when all vacuum fails is to defrost vents. Most likely your vacuum supply to the switch is weak. Check the connection of the supply line to the intake manifold for damage. If no problem there, trace it to the switch on the control panel. If there is an accumulator, make sure it isn't leaking and is storing vacuum. If all this is good, look at any other vacuum lines connected to the intake manifold that may be leaking and possibly reducing the vacuum supply to the HVAC control line. Let me know if you have more questions.
Repair Help & Product Troubleshooting for 2006 Chevrolet Silverado 2500HD 2WD
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