ive had my blazer for a year and a half now. so i dealt with this issue last year and wasnt able to find what it was that was doin this. every air option works except for the floor air vent option. in past vehicles, thats my choice to use majority of the time. ive went thru the vaccuum lines and they are all hooked up. any ideas on what could be causing this?

 

A bit of advice, Always include your vehicle information when posting (year, make model 4wd, 2wd etc...)
Is your model the automatic climate control or manual?

If manual, I would suspect a actuator is stuck. You should use the search feature of this forum as I've seen many posts regarding vent issues for the Blazer. Attached is a schematic from this forum that may help. Let us know what you find out.

 

Don't know if it's manual or automatic climate. I'll try the actuator, so thanks for that lead. As for what my ride is, sig pic tells u....