When you start the vehicle there is a loud knocking that goes on for about 1 minute. There is no air coming from the front vents. What is the thing that shifts the vented air around? I wonder if it has somehow become jammed? Air works from floor and windshield vents.
GMC Q&AAsk Your Question
2003 GMC Envoy Question: Loud knocking in dash when vehicle is started and no air from front vents.
Answer #1Greg's Orange Auto (10955 Answers) , Orange, CA - (714) 361-9355globalhelper November 01, 2012, 06:05Master
your blend door sctuator has gone bad, that regulates air flow from heater to defrost and a/c. approx cost is 400.00 to replace it.unless its the one that is in the middl of the dash and that one is approx 800.00
csubak30 November 01, 2012, 06:07Master
Loss of use in the HVAC directional vents will usually mean a bad mode actuator that needs replaced.
Answer #3your.mechanic November 01, 2012, 08:19Master
the blend door broke off...and is flapping inside the car.
Replytmlamon, November 01, 2012, 17:39Rookie
I wonder if there is a way to reach in and remove the broken part without pulling the dash. Not really concerned about the vent but the knocking is pretty annoying.
Replyyour.mechanic, November 01, 2012, 20:21Master
There is a way to eliminate that annoying knock, try to access where the door or actuator is and use self-tapping screws to wedge whatever is making noise.
Replyglobalhelper, November 02, 2012, 05:44Master
this swill stop the noise nut not fix the problem