Air out of all Vents

[Needhelp]

I have a 2002 Gmc Sonoma 4.3l and the issue is When i turn on the heater/ac control it blows out of all the vents no matter what the setting is on. any ideas? as this is annoying blowing in the face at all times

 

[lmleck]

Check under hood between brake booster and firewall for split vacuum hose or hoses.
Rotted vacuum hoses in this area is common, as I found on my '03 sonoma.
Be sure to find the one that is connected to the vacuum reservoir in the fenderwell behind the abs system.

 

[Needhelp]

Ok all the Vac lines there look good but there is one hose that goes into the fender that looks kinda old but not sure how to get to it as it goes into the fender on drivers side

 

[lmleck]

It goes to the vacuum reservoir. There is a port sticking out behind the abs controller.

 

[Needhelp]

Ok need to add when i switch to say Defrost it blows on the defrost and just the front vents but no floor. If i switch to floor it blows on the floor and front vents. so i guess it is switching but for some reason the front vents are the ones always blowing air. Would this still be a vacumm issue?

 

[lmleck]

Could be a leaky vacuum motor or hose under dash leaking vacuum causing upper vents to stay open.
Do the other outlets open quickly or slowly...

 

[Needhelp]

like if the dial is on floor and i move to defrost it takes like a couple secs for the air on floor to stop blowing