whats causes you air to blow through the defrost duct? defrost, vent, a/c everything blows through the defrost vent at the windshield. any ideas???

 

When you have a vacuum loss the system defaults to defrost. Check the fitting that goes into the firewall behind the battery. It tends to break.

 

ok it goes into the fire wall right?

 

i see a little line that goes through a big hole in the firewall and it comes up to a T and oneof those hoses goes to another T. all of them look good

 

i am a new member and noticed this post....Are you still looking for a solution to fix your problem? Does your truck have the EATC which is the electronic climate control? in other words all push button and no *****. if so i can help you out.

 

yes all push buttons and no ***** except the little roller that turns the fan up and down

 

http://www.f150online.com/forums/hva...buildable.html

see if this link helps anyone with there climate control. it fixed mine.