Air control unit only blows air on #4 on 2007 Chevrolet Colorado

Numbers 1,2, and 3 are out. Only #4 blows air. How can i repair this?

1 answer 1 comment
I WOULD BE SUSPECT OF THE BLOWER MOTOR RESISTOR . ITS NEXT TO THE BLOWER MOTOR
it is the P.O.S. wiring harness.