Air flow only comes through the vents after battery disconnect

SOURCE: AIR VENT PROBLEM

Chevrolet 2003 TrailBlazer

For a digital air flow system try resetting the HVAC unit. Either take out the fuse for the HVAC module or disconnect the battery for 5 or 10 minutes. Reconnect battery or replace fuse. Turn the ignition to ON and DO NOT STARTor ATTEMPT to START ENGINE !!. You should hear the actuators, motors etc resetting. This should take about 2 minutes . Then you can start engine. If this does not work, you may have a bad actuator under the dash.

SOURCE: no air flow thru ac vents

sounds like your directional door in you air box under dash is not working.test with tested while moving controls.check for current.

Jeffrey Turcotte

• 8991 Answers
• Posted on Sep 28, 2010

SOURCE: 2005 Silverado 2500HD 4WD -

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.

SOURCE: air not flowing through dash vents in chevy classic

Cables from contol to vents not working.