Just like the title says. 99% of the time it will blow out of the vents in the dash. Every once in a while it will switch to defrost or to the floor but not very often. I mostly keep the switch in the defrost position but once it starts blowing out of the defrost I can blend and it will do partial floor and defrost. Once the truck is shut off it will go back to the dash and not switch to any other position. Of course it will not switch when really needed for snow or rain. Any thoughts?

 

Exact same problem I had earlier last year; the almighty blend and mode door along with door motor issues was the cause of mine; quiet a big problem with these things; lots of posts about them. Some other guys on here could tell you where to start; I went to the dealer with mine and it still took them 2 dives into the dash to get it right; it is an absolute miracle that my dash doesn't rattle like a soup can full of rocks with them in and out of there

 

keep the fan on lowest setting when switching to defrost it doesnt have enough juice to turn the doors and it will work be careful with the dials as well!