won't shift from defrost

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Jul 23, 2010 | 08:55 PM

hog creek work truck

Thread Starter

Mountain Pass

Joined: Jan 2008

Posts: 125

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won't shift from defrost

I just got a 1993 f150 the blower works but it won't shift off of defrost the **** on the blower feels like it turns to every notch but doesn,t change the air flow.Is there a common problem with this I should check?

Jul 23, 2010 | 09:24 PM

parr4

Elder User

Joined: Dec 2000

Posts: 570

Likes: 1

From: Austin Texas (area)

Defrost is the default position of the system when there is a vacuum leak to the air-direction motor. Check for loose/broken vacuum hose.

Jul 23, 2010 | 11:02 PM

Franklin2

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Joined: Jan 2001

Posts: 56,979

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From: Virginia

Your main vacuum line goes through the firewall over on the pass side under the hood. It should go across and hook to the engine or the vacuum tree on the firewall behind the engine.

Jul 25, 2010 | 12:24 AM

phurst

Senior User

Joined: May 2010

Posts: 302

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From: Richmond, VA

Mine had the same problem. Ended up being the little control box the lever connects to on the back of the HVAC controls. This is the thing I'm talking about.