AC Dash Vents

I own a 98 GMC Sierra 1/2 ton. I cannot get air or heat to blow out of dash vents. Blower motor works on all setting. The temp control works. When I go to switch position from the defog to dash vents it makes a noise like it switching but no air comes out of the vents.I bought a new blower motor control system $130.00. It is all electronic with no vaume lines, I plugged it in. Still no air comming out of vents. Any help appreciated.

when you replaced all these things did you try the unit when it was disasembled to make sure nothing is blocking the airflow, that would be my guess

On my 90 K1500, when I could not get air to come out the defroster, it was the mode actuator. The actuator controls where the air goes.

I took it apart and added some grease to the gear and put it back in. Did this a few months back and it is still working.

On my 90, the mode actuator is above the tranny hump under the dash. Not sure where it is on the 98.

//2000CAYukon