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Old Jun 10, 2009 | 12:30 AM
  #1  
priester68's Avatar
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Question Help with a/c

I have a 2003 Ford F150 Lariat 4x4. The a/c in the truck has the auto feature whatever that is. My problem is, the only setting I can get cold air to blow out of the main vents is PNL FLR. If I cut it on auto, or Max AC it blows out of the dash vents like it's on defrost. This is very aggravating. Can anyone suggest a quick fix or am I in for major surgery to fix this? Thanks very much.
 
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Old Jun 10, 2009 | 06:37 AM
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Either one of the vacuum motors has failed or, more likely, the EATC control unit has failed.

Possibly there is a small vacuum leak in the supply to the system that is preventing it from being able to fully activate the vacuum motors. If this is the case, then you'd usually notice airflow diverting to the defroster outlets, especially under heavy acceleration.
 
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Old Jun 10, 2009 | 09:47 PM
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Originally Posted by projectSHO89
Either one of the vacuum motors has failed or, more likely, the EATC control unit has failed.

Possibly there is a small vacuum leak in the supply to the system that is preventing it from being able to fully activate the vacuum motors. If this is the case, then you'd usually notice airflow diverting to the defroster outlets, especially under heavy acceleration.
Agreed. I've also been reading of a number of EATC issues caused by a cracked vacuum solenoid for the front hubs on 4x4 trucks recently. It usually causes the system to default fully to the Defrost ducts, but... Check out the recent postings in this forum and see if it fits.
Since you can get it to work correctly on PNL FLR, I also suspect the EATC unit.
 
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Old Jun 10, 2009 | 11:17 PM
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Could also be a bad vacuum actuator. These are the little silver cans under the dash that pull the air direction doors around from one position to another by the action of vacuum on a diaphragm inside it. Often hard to get to but easy to test. I haven't looked into them in this vehicle yet, but had a bad one in a previous Ford.

-Dave
 
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