Would love some help with A/C blowing out wrong vents

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07-07-2013, 11:25 PM

mgood777

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Would love some help with A/C blowing out wrong vents

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What I have noticed is that when I put the engine under a load (like accelerating or going uphill) and then release the load (take my foot off the gas), then moments after I release the load the problem will correct itself and the cold air will come from the dash vents like it is supposed to. Everything will be OK for a few minutes, but eventually it switches again and the air will go back to the defrost vents.

I can repeat this anytime I want while driving down the road. I hit the accelerator and then let off, as I let off the gas the air comes back to the dash and then it eventually goes back up to the defrost vents again.

One time several years ago I a similar problem, except at that time the air was always coming from the defrost vents. I did some research and found a broken vacuum line between the vacuum reservoir (on the back of the battery box) and the firewall. I fixed that leak and it solved the problem. This time I replaced that entire vacuum line from the reservoir to a check valve in that line just before the firewall, including replacing that check valve. This time it did not solve the problem.

If anybody has any advice about how to diagnose or fix, I would much appreciate it. Dealer will charge me a boatload to fix what I’m afraid is a simple vacuum leak. I’m not above spending a little money and time to replace a bunch of vacuum lines on the hope that it will fix a problem (like I did with the one I just described) if that’s what it sounds like to somebody, but I really don’t know where to start to begin to diagnose it.

Any help is much appreciated. Thanks a million.

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07-08-2013, 07:11 AM

projectSHO89

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You have a vacuum link. See HVAC FAQs, link below.

If you have EATC, include its o-rings as possibilities.

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07-08-2013, 05:47 PM

steve(ill)

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https://www.ford-trucks.com/forums/8...e-defrost.html

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04-25-2014, 01:24 PM

tdogultra

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I have the EXACT same problem that mGood777 is having. I drive a 2003 F150 Harley-Davidson Edition. I took it to the dealer to have it diagnosed, they told me that all the vacuum lines are OK, but the Climate Control Head is not holding vacuum. They then said that the Climate Control Unit needed to be replaced. I'm OK doing this, but was just curious if anybody knows where to find a less expensive part or if I can rebuild the one I have. The Ford dealer here in Central Illinois wants $963.00 just for the part, not happening!! He did give me the part number, but the printout isn't very good, so I'm not sure if this is correct or not. 3L3719989AA

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