Air Control switches to defrost on its own

[SHOByrds]

my heat or ac will switch to defrost if i turn it above low
whats the prob?

 

[turbosho]

I have this exact issue, TTT anyone have an idea?

most cars this would be a vacuum issue, but I can not find a leak. Is there an online vacuum diagram?

 

[JRA2000TL]

My brother's car has this issue; I heard there's some kind of diaphram behind the dash that's not working correctly. If you can't find a vacuum leak at one of the colored lines, I think this would be this issue. I don't remember all the details though. I know his hasn't been fixed yet, but he wants to get around to doing it. Anyone ever replaced one of these? I think you do have to pull the dash back but not totally out.

 

[SHOByrds]

i heard it is the blend door

 

[turbosho]

digging around today i fixed mine.

open the glovebox all the way, and on the left side there are 3 vaccum actuators. on my car the arm that goes to the middle actuator had broken.

I temporarily wired the door open until i can find time to remove the dash to replace the broken door.