1997 GMC Sonoma - Everything coming out defroster?

[nick]

No matter what I turn the heat/air on it comes out the defroster vent. Nothing comes out the vents on the dash and nothing comes out for the floor. Everything comes out the defroster. The heat comes out the defroster. The air (which isn't cold) comes out the defroster. The defroster comes out the defroster. I would really like to know what might be the problem! Thanks.

[zebadee]

their are some flaps that are not closing or opening to control the flow of air.

[rockindel1]

I am not sure which control system the sonoma uses it is either
vaccuum or cable
so either a control cable has disconnected
or a vaccum pod is lost its vaccuum
or one of your "door actuators" is stuck (vent doors)
good luck

[BIG-G]

a vacuum hose or hoses most likely.

[Molson02536]

Originally Posted by nick

No matter what I turn the heat/air on it comes out the defroster vent. Nothing comes out the vents on the dash and nothing comes out for the floor. Everything comes out the defroster. The heat comes out the defroster. The air (which isn't cold) comes out the defroster. The defroster comes out the defroster. I would really like to know what might be the problem! Thanks.

The vent actuator is vacuum controled. The switch it self is like a valve and may have gone bad or just dirty, inspect the switch in the dash and inspect the vacuum line on the drivers side by the brake booster. There are vacuum line's there and it's common for the line to have a leak where the T connections are.

Good luck and keep me posted, be glad to help you get your vent switch working again soon. This is more common with the 4X4 Jimmy's/Blazer's, and Sonoma/S10 due to a faulty 4x4 vacuum switch on the transfer-case leaking transmission fluid in to the vacuum system.