I have a 2009 f150 4x4 crewcab with the texas package and tow package. The other morning after an ice and snow storm I tried to defrost my windshield and although I could hear the blower blowing air no air was going through the vents to the windshield nor would it change to the floor or dash vents. Finally I scraped enough ice off the windshield to drive down the road and then it began to work correctly. Do you have any idea why it would not work while I was trying to warm it up in my driveway?

 

Did you push the defrost button on the HVAC panel? There's a specific button that gives you full defrost.

 

Yes,I did press the defrost only button and it would not come on. I also pressed the floor only button and all other cokmbinations for the heater/defroster without success until I started driving down the road and it finally started working. I am wondering if the frozen rain which got down in the outside vents at the bottom of the windshield might have caused the cylinoid or whatever to freeze or plug up. I do not know but I thought that most of the accessories were inside under the dash and protected from the weather.