Hi everyone. I have an 02 blazer LS with manual climate control that never turns off. With the rotary switch in the off position, the fan blows the same as if it was on and the fan speed switch was in the first speed. In addition to that, the air blows out of all of the vents regardless of the position of the rotary ****, even in off. My guess is maybe the airflow direction switch is stuck in on position even if the **** still turns. Or I was also thinking that maybe the valve that the switch controls to channels airflow to the proper vents may be stuck. the temp control **** works fine- hot air on hot and cold air on cold. the fan speed switch also does its job fine. There is no clicking noise coming from it like I know some vehicles do. How should I go about trouble shooting this? Thanks!

 

Vacuum lines, check them all! Every one, even if it doesn't lead to the cab or the box in the DS fenderwell. Any vacuum leak will cause the air to come from other vents other than what you selected.
I'm confused thigh... "With the rotary switch in the off position, the fan blows the same as if it was on and the fan speed switch was in the first speed."
& then you said ... "the fan speed switch also does its job fine."

So which is it?!
It could also be a blend door issue, but the cheapest way & easiest is to check all the vacuum lines. Look for excessive cracking, disconnected lines etc.
One way I use (other than just visual) is to let the engine idle & spray brake cleaner on the lines. If the engines' idle changes - you've found a leak.

P.S. try searching in here for climate control issues or vents etc... change up the wording, sit back & read on. Lots about this is covered in here in a LOT of posts. Just look at New Posts every now n then & you'll probably see some.

 

THanks, heres some clarification where u were confused. The fan speed **** does not have an OFF position its just 1-2-3-4. What I mean by the air blowing the same is this. IF i have the rotary switch in any of the modes AC,defrost,floor, whichever, and the the fan speed switch in in one, it air comes out of all of the vent just the same as when the rotary **** is turned to the off position when there shouldn't be any air coming out at all. But I know that the system is off because when i turn the fan switch to 2-3-or 4, it doesnt do anything. Hopefully this makes more sense.