Help with HVAC vent selector
 

Hey all,

I'm having a problem in my 94 accord lx with the fan selector. When I push the button for air to come out of the top vents (from nothing being selected), the air only comes out the two side vents (driver and passenger) and the lower vents. All the other selectors seem to work fine. Does anyone have any idea what would cause the upper vents to not turn on properly? Thanks!