Problem: A/C blows through defrost vents!
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Senior User
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From: foot hills
Problem: A/C blows through defrost vents!
I've searched for an answer for the last couple days but haven't found anything concrete. A few days ago the A/C started taking a minute or two to transition from the defrost vents to the A/C vents when first turned on. Then it got to the point where it would make a fluttering sound (blend door?) for a few seconds and then transition. Now it just blows through the defrost vents and never comes through the A/C vents. I've taken the glove compartment out and fiddled with the vacuum actuator but that seems to control just the heater function. Anyone have any ideas how to get to the A/C blend door? Thanks
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Joined: Jul 2006
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From the HVAC section of the forums:
Problem: Air flow has defaulted to the defrost vents (either all the time or under acceleration).
Solution: The system is designed to default to the defroster in the event airflow control is lost. Intake manifold vacuum is supplied to the control head, whether manual or automatic (electronic) to operate the vacuum motors.. A very common failure is a split, cracked, or otherwise leaking vacuum line located between the battery and firewall. Other causes include a leaking vacuum reservoir (inside the right front fender), faulty check-valve inside the dash, or other vacuum leak in the system.
Problem: Air flow has defaulted to the defrost vents (either all the time or under acceleration).
Solution: The system is designed to default to the defroster in the event airflow control is lost. Intake manifold vacuum is supplied to the control head, whether manual or automatic (electronic) to operate the vacuum motors.. A very common failure is a split, cracked, or otherwise leaking vacuum line located between the battery and firewall. Other causes include a leaking vacuum reservoir (inside the right front fender), faulty check-valve inside the dash, or other vacuum leak in the system.
Posting Guru
Joined: Oct 2003
Posts: 1,198
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From: Tulsa, OK
90% chance this problem relates to your 4x4 auto hubs. This happened to mine. Check the vacuum switch on right front inner fender. This cracked on mine and allowed a huge vacuum leak so that vacuum pump could not keep up. Caused exactly the same symptoms you describe.
Hope this helps.
Hope this helps.
Posting Guru
Joined: Dec 2007
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From: Metro Detroit, MI.
Hey, I'm in the same boat. A/C only through the defrost default section. Anyway can someone can take a picture of the inner fender location so I can check mine and replace. Leather, tinted windows, and failing A/C doesn't work well for me.
Postmaster
Joined: Aug 2003
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From: South Texas
Check the small vacumm lines that run next/under the battery and to the pasengers side firewall. My F150 has a line crack at a connection at the firewall. Dealer wanted $120 to fix it, it cost me $5 and less than 10 min. to fix it. The hardest part is finding the leak.
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Senior User
Joined: May 2003
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From: Mobile, Alabama
Problem:A/C blows through defrost vents!
Happened to me last year. I just had the lines capped and was going to get it fixed later. The locking hubs didn't work, but the A/C Cooled fine.
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Senior User
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From: foot hills
I checked the 4wd and it still operates just fine; therefore the vacuum pump is good. I read through the repair manual at AdvanceAuto and from the looks of it I don't really want to rip into the dash. As much as I hate it, this may be a job for the repair shop.
Postmaster
Joined: Aug 2003
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From: South Texas
Chances are the vacuum leak is under the hood. Try what I did, I took mine to the dealer for some service and had them check out the A/C problem while it was there. Told them to fix it if it was covered under warranty, or call me first if it was gonna cost me. (I knew the warranty had just expired, but hey you never know!) Sure enough they callled, and they said is was a vacuum line. Told the dealer, just to leave it alone, they charged me $30 bucks for the A/C check. Looked under the hood when I got it home and it was easy to spot where they had been checking the lines because my engine bay was dirty and they had wiped off the lines they where checking. Spotted the broken line and spliced it back together with some rubber hose and silicon.
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