[Spitfire7175]

it could be a problem with the switch, or a vacuum leak, but it could also be that the doors that control the flow of air are stuck in one position. you should check for vacuum pressure at the switch, if there is none then you know its a vacuum leak. when you turn the switch you should hear a hissing sound for a couple seconds as the vacuum takes effect. (if you need help accessing the back of the switch just ask.) if you find there is vacuum at the switch then the switch is bad, if not then you have to find your leak and fix that