Question about 1999 Ford F150 Regular Cab

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Switch on dash won't change direction of air to vent, etc.

I have a 1999 F-150, 4.2L, V-6. The switch on the dashboard that controls the air direction to the vent, floor, defrost, etc. sends all the air all the time to the defrost. The other switches work fine. Can you help me?

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  • Ken Mifflin Feb 26, 2009

    You were very helpful. The hose going to the firewall had a hole in it. I replaced the line. However, my problem still exists. Everything goes to defrost. I had a check engine light come on recently that I was troubleshooting. I think the vacuum hose may have solved that problem.

  • Ken Mifflin Mar 08, 2009

    You were right on. I fixed the main problem and caused the other when moving the hoses around. Everything was tightened up and all works fine. Thank you again.



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You have a vacuum leak,defrost is the default postion,no vacuum to controls. Check the small black vacuum line that goes thru the firewall on the passenger side of the firewall and trace it back to see if you can locate a leak. It will go to a vacuum resivior then to the intake manifold.

Posted on Feb 16, 2009

  • Chuck Martin
    Chuck Martin Feb 26, 2009

    you still have a vacuum leak though it may be inside the vehicle at the controls or one of the vacuum motors.Pull your controls out and make sure you have a good vacuum to black line there.



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