# Why is a/c blowing out of defroster?



## Elite Property Services (Oct 28, 2008)

I have a 2003 F250 when I turn the a/c on it blows out of the defroster. Mechanic told me vacuum was fine and he wasnt sure what it could be. I still think its vacuum because sometimes when applying the brake it will switch to vents. Any ideas? Thanks Nathan


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## drp (Oct 12, 2009)

vacuum leak. Heating system defaults to defrost with a vacuum leak. Most common location 4wd auto hubs. Check if it will engage the hubs when set on auto.


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## lotec25 (Jun 10, 2008)

is it just blowing out of the Defroster? or is it coming out of the regular vents? What does changing the controls do anything? Does heat still work?


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## Elite Property Services (Oct 28, 2008)

lotec25;1052118 said:


> is it just blowing out of the Defroster? or is it coming out of the regular vents? What does changing the controls do anything? Does heat still work?


I am still looking. It is blowing out of the defroster only no change when control switched to any position heat or a/c. Thanks Nathan


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## lotec25 (Jun 10, 2008)

vacuum leak for sure then, check all the vacuum lines. The controller is all vacuum controlled, Weird that it will kick over when you apply brakes though.


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## Elite Property Services (Oct 28, 2008)

lotec25;1052146 said:


> vacuum leak for sure then, check all the vacuum lines. The controller is all vacuum controlled, Weird that it will kick over when you apply brakes though.


It has only kicked over a few times when applying the brakes and when it did it shuttered like it was hesitating to switch. Is their any way to narrow the search down for the leak?

Thanks Nathan


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## lotec25 (Jun 10, 2008)

drp;1051844 said:


> vacuum leak. Heating system defaults to defrost with a vacuum leak. Most common location 4wd auto hubs. Check if it will engage the hubs when set on auto.


start here? does the hugs engage? if so, just a process of looking for worn out vacuum hoses. Not much i can think of but check the hoses man.


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## Elite Property Services (Oct 28, 2008)

lotec25;1052162 said:


> start here? does the hugs engage? if so, just a process of looking for worn out vacuum hoses. Not much i can think of but check the hoses man.


Yes i wll keep looking


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## bluerage94 (Dec 24, 2004)

Do you have the electronic climate control?


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## Elite Property Services (Oct 28, 2008)

bluerage94;1052229 said:


> Do you have the electronic climate control?


No i don't. Don't those have an o-ring problem?


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## Silverstreak (Oct 25, 2007)

yeah vac leak, the conroller for the vent is right under the glove under the dash (or maybe you gotta take the glove door partway out..i forget) there is a vac-actuated valve that pulls the air deflector to the vent position, you can wire tie it halfway until you figure it out, or something might have disconnected the vacuum tube off the actuator


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## TBElectric (Aug 26, 2010)

The vacuum line in the engine compartment which is white in color is either broken, sretched, or cut allowing a vacuum leak. It is located on the passenger side of the engine bay nearest the firewall. It usually runs behind the a/c dryer assembly. Hope this helps.


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