AC switching modes

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May 6, 2014 | 07:43 PM

07Cruzer

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Joined: Oct 2007

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AC switching modes

Hey everybody, 06 F250 gas King Ranch. My AC wants to switch modes on its on. I can have it on vents & it will go to defrost then back to vents every few minutes. Any clues? Air is cold.

May 6, 2014 | 09:51 PM

Mike189677

Fleet Mechanic

Joined: Jan 2012

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Vacuum leak. Check the vacuum lines coming from the auto hubs up to the vac pump if you dont find cracks there start following the vac lines under the hood.

May 7, 2014 | 05:21 AM

redford

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Joined: Sep 2000

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From: Stephensville WI

The heating system uses vacuum to move things. When there is insufficient vacuum to drive the system, it reverts to blowing out the defrost vents.

May 7, 2014 | 12:43 PM

07Cruzer

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You guys are exactly correct! I was at work when I posted the original message. So today I checked under the hood & sure enough the small vacuum line 1/8" OD maybe on the passenger side maybe was off. It's loose so I'll replace it. But the drive home it stayed in the vent selection.

Thanks again.
Ronnie

May 7, 2014 | 07:56 PM

Lubbockguy1979

Cargo Master

Joined: Jan 2009

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From: Lubbock

Ok next question.... how can I make the recirculate the default hvac action and fresh air by selection only on the digital climate control? I typically remember to switch it once behind a stinking vehicle or other foul odor