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Air blows from defrost only

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Old 06-02-2010, 09:20 PM
Podaso Podaso is offline
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Air blows from defrost only

I know there's been posts about this but I've been unable to find them...if anyone has a link in this forum, please let me know...

I checked the HVAC section too to no avail. When I put the control **** on 'Panel', air blows from the panel and the defrost. When on 'floor' it blows from the floor and the defrost, etc... Is this a vacuum issue or a blend door issue, or am I way off?

Any ideas/prior threads would be appreciated.

'98, 5.4, 4x4, 136,000 miles, anything else?
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Old 06-03-2010, 07:00 AM
projectSHO89 projectSHO89 is online now
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It's a vacuum problem, specifically, a distribution selection problem.





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Old 06-03-2010, 11:45 AM
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The dash switch (e.i. a/c, panel,off, defrost, floor, defrost/floor) has the vacuum lines on the back of it.Check there first (cheapest with less hassles). Otherwise I would say the problem is in the heater box with the blend door
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Old 06-03-2010, 06:36 PM
skiatookbandman skiatookbandman is offline
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What I'm seeing is a single vacuum line coming through the firewall and into the cab. Is this schematic refering to the cluster of vacuum lines and junctions located between the battery and firewall. On my Expedition I do not have vacuum lines that come into the rear of the control panel. Rather, there are three wire clusters.

Thanks for everyone's input... very friendly forum.
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Old 06-03-2010, 08:47 PM
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Quote:
Originally Posted by RED02FX4 View Post
The dash switch (e.i. a/c, panel,off, defrost, floor, defrost/floor) has the vacuum lines on the back of it.Check there first (cheapest with less hassles). Otherwise I would say the problem is in the heater box with the blend door
It cannot be the blend door since the blend door has no effect on where the air comes out.

The vacuum schematic is for the F150 with a manual climate control head. That single vacuum line through the firewall is represented on the diagram by the line that goes from the junction at the reservoir and the check valve to the function selector switch. That line is not your problem. if it were, you'd get airflow out of ONLY the defroster vent.
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Old 06-03-2010, 09:17 PM
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look at the schematic above on the far left. lower corner is the controler and upper area shows the defrost - vent- floor doors. they are controlled by vacuum from the control ****. if you always have defrost, but get flows to additional areas also, then you have a stuck door, or vacuum leak inside the controler block.. i would guess leaks inside the controller between sections.
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Old 06-03-2010, 09:45 PM
skiatookbandman skiatookbandman is offline
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My screw up... I posted in the wrong area of the forum. My vehicle is a '98 Expedition with dual air. Any help there would be great.
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Old 09-05-2013, 05:07 PM
mikeinaz mikeinaz is offline
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air blows from defrost only

My 2002 Ford Ranger had this exact problem so I started tracing vacuum lines and found the vacuum hose to the reservoir had contacted a hot surface and melted. I cut out the damaged section and spliced with a piece of tubing and the problem went away. I would like to thank all here for adding to the knowledge base as any info seems to be hard to find on these trucks.
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Old 08-02-2016, 12:11 PM
Max Dugas Max Dugas is offline
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Quote:
Originally Posted by projectSHO89 View Post
It cannot be the blend door since the blend door has no effect on where the air comes out.

The vacuum schematic is for the F150 with a manual climate control head. That single vacuum line through the firewall is represented on the diagram by the line that goes from the junction at the reservoir and the check valve to the function selector switch. That line is not your problem. if it were, you'd get airflow out of ONLY the defroster vent.
I drive a 2000 HD f150 and my air blows through ONLY defrost. No matter if I put it on any selection. I always keep it on max AC, but it randomly just started blowing out of the defrost only, any help is appreciated!
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2002, 60, 98, air, blows, defrost, defroster, e450, expedition, explorer, f250, ford, sport, truck, vents

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