Defroster to AC won't switch - Ford Powerstroke Diesel Forum
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post #1 of 5 Old 06-18-2014, 11:48 AM Thread Starter Rookie
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Defroster to AC won't switch

I have a 06 F-350 Super Duty 4x4 short bed dually and the air is not working right most of the air from the blower is going out the defrost vents on top of the dash if I turn the fan on low it will make a noise like it is opening but as soon as I turn the fan on high it blows the majority of the air out the defrost I have checked my vacuum pump under the hood and it works and I have even checked the plastic hoses behind the glove box and they are good can't figure it out and it is getting hot need some cool air any ideas or suggestions.
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post #2 of 5 Old 06-18-2014, 12:28 PM
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Your vacuum hubs are leaking. The HVAC box in the cab has vacuum operated diverter doors that will default to defrost if no vacuum is present. If you don't use your auto hubs, you can try to plug the lines that follow the radius arms forward to the front axle.

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post #3 of 5 Old 06-19-2014, 04:54 AM
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When I did my coolant filter install I some how unplug a vet small vacum line right up against the fire wall on the passenger side. Truck was doing the same thing yours is. Once I found that and replaced it the problem went away.

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post #4 of 5 Old 06-25-2014, 11:46 AM Thread Starter Rookie
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Well I checked my vacuum lines and there is no leaks I turn the key on vacuum motor comes on and runs for a few minutes and shuts off like it is supposed to when holding vacuum. What else could be causing this to happen?
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post #5 of 5 Old 06-25-2014, 12:19 PM
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the actuator behind the glove box door
you can open the GB door past the stop and look around you can even manipulate the actuator by hand to see what it does

the vacuum hubs or lines to the hubs can leak and it will only effect the vents for less than a minute
as soon as the PVH solenoid stops sending the signal it should shut off the vacuum to the hubs resuming HVAC function now if that solenoid has failed and you have a problem past that then yes it can be a leak but it has to involve the bad solenoid to be a permanent issue

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