2005 Chevy Colorado

Hello my name is markoz cortez have a? About my chevy colorado; the problem is that the stwich of a/c controller it only work on #4 wich is the maxim on 1 -2-3 dont work like a said only works on 4 all the heater and A/c works fine so. Am wondering whts wrong with it, what I suppost to change of it. Thank you and I hope to hear from you soon thanks again