Air flow control stuck on defrost

gmc
jimmy

#1

my switch to control the direction of the air is stuck on defrost so i cant move it to like feet or face whats wrong and how do i fix it?


#2

Year, make, model? If it’s a vacuum operated system, look for a hose unhooked somewhere. Does your idle happen to be slightly higher? My son was parked outside with grandma’s Corsica. Idle was high. I said, “Son, don’t you see that as “unright”?” …he goes, “Oh …yeah, I guess”. “How long, son?” …“a few days, I think”. “Isn’t that something that triggers some lightbulb in your head?” “Well, sorta.” Drove with him later, noted that all air came out heater duct. “Son?” “Yes, father?” “didn’t you notice that all the air comes out the heater duct?” “Oh, …yeah” “Didn’t that trigger some warning light in your head that something was ALSO unright?” “Well, …yeah.”

I found the detached vacuum line. Idle and doors fixed. Son still broken for a couple of years.


#3

They’ve been making the GMC Jimmy for quite a few years. How old is yours?


#4

97


#5

97 gmc jimmy


#6

Is it stuck on defrost or does it flip to defrost upon heavy gas pedal usage? the latter is the sign of a lack of vacuum to the HVAC system, now stuck always is a different story.


#7

You actually said that the switch was stuck - so are you saying that the actual control won’t move? Or that you move it, but it doesn’t change the airflow? Is it a slider or a dial? If the switch itself is mechanically stuck and won’t move you’ll need to pull the console from the dash and inspect.


#8

I am going to guess it is not that you can’t move the control off defrost, but that no matter where the control is, it is working in defrost mode.

Defrost mode is the default mode because if it is going to fail, you want it to be defrost for safety reasons.

I would look for a loose, detached or damaged vacuum hose first (assuming your car uses vacuum controls.)