so ive had this problem a couple times, my heater vents wont adjust, i get a hissing sound out of the control on the dash, and all i get is air out of the defroster. i replaced all the vacuum lines under the hood, i replaced the vacuum control switch in the control panel and it still happened...wound up being that the heater door was stuck, like the actual hinge was stuck...simple fix, took off the trim under the dash, removed the heater box cover and then re-positioned the heater door, put it all back together and success!

but it seems to keep coming out of its position, i have tried putting the screws in tight to make sure that nothing pops out again, instead the door didnt move properly, i tried putting the screws in loose to make sure it could operate properly...no matter what i do the door seems to get jammed ever once and a while.

does anyone else have this problem? if so how did you fix it? cuz im getting a bit tired of taking apart the dash to fix this small problem lol, but its annoying to drive and just hear 'hssssssssssssssssssssssssssssssssssssss' for up to an hour...and then the sound gets stuck in my head and no matter how high i turn the radio, i can still hear the sound in my head cuz i know its still happening which still annoys me lol. yeah, i know, i might be slightly crazy, and yeah the voices talk to me sometimes but i just want to fix this problem once and forever

 

This may not help you but I wanted to suscribe anyhow.When I removed my a/c and the heater control bypss valve or whatever you call it I cut that small vacuum hose back at the harness by the trans dip stick.The rubber caps I put on it kept cracking and the heat would default to defrost.Capped it with viny one and its lasted longer.My door does nt operate either and I dont know why.I only have heat and defrost which is fine cause a/c is gone.Just wonder why my doors messed up.

 

default defrost is what happens when there is a vacuum leak...id suggest starting from your vacuum canister (under the battery in the fender) trace the vacuum lines and see if you can find any that are cracked, or if you have a friendly enough person at the front counter at your local parts store (like i do) then they'll just give you the like 4-5 ft that you'll wind up needing.

this sounds like your vacuum lines are busted, mine are brand new, but this doesnt happen all the time, just sometimes. its like the door gets stuck.

 

Well My vaccume lines have been replaced and heat and defrost are working.I was just trying to offer a lil help.My door however,doesnt seem to be operating properly but I dont need the vents to work.Defrost and heats enough for me.

 

true, i just figured seeing as how its got everything in the car, i want everything to work...for instance i dont really NEED that swiveling map light on the top center t-bar console to work, but it annoyed me that it had power and no light coming out of it so i took it apart and fixed it just cuz it didnt work lol. same is going for the vents, it blows on the floor, and on the vents and on the defrost, but sometimes it just sticks and hisses until i fix it