My heat or a/c will only blow out the defrost, i would think its the vacuum lines but i have no diagrams to even get started on that. 5.2 318 v8

Works on vacuum check you hook up behind the heater controller

No vacuum controls on this system . Electronically controlled mode door actuator . (electric) You mite find a video on youtube for replacing mode door actuator .

I think the flapper doors operate on vacuum. Could be that as engine warms some engine part changes its setting and swaps to a vacuum line which is leaking. Also possible a flapper door actuator has small leak. Use vacuum gauge to check and see if something changes vacuum at same time error occurs.

the heater vacuum motor and lines needs to be checked.Also get the blend door checked.

NO HEAT ON FLOOR VENTS

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As per your problem mentioned. There are few solved help links to troubleshoot these problems. Go through the list and Click the link below:----

2000 Toyota Avalon: No heat on Passenger Side?

http://whatisbyme.blogspot.in/2012/05/2000-toyota-avalon-no-heat-on-passenger.html

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No heat on Oldsmobile Silhouette?

http://technoanswers.blogspot.in/2012/02/no-heat-on-oldsmobile-silhouette.html

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Heater blows cold?

http://schematicsdiagram.blogspot.in/2012/02/heater-blows-cold.html

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Heat blows cold on drivers side and hot on passenger side?

http://schematicsdiagram.blogspot.com/2011/12/heat-blows-cold-on-drivers-side-and-hot.html

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Hot air on the driver's side vents only?

http://repairhelpcenter.blogspot.com/2012/01/hot-air-on-drivers-side-vents-only.html

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Temperature gauge does not move and no heat when heater is ON?

http://technoanswers.blogspot.com/2012/01/temperature-gauge-does-not-move-and-no.html

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1992 Toyota Camry: A/C Control light Flashing and A/C not Blowing Cold?

http://technoanswers.blogspot.in/2012/04/1992-toyota-camry-ac-control-light.html

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No heat, blower blows only cold?

http://technoanswers.blogspot.in/2012/02/no-heatblower-blows-only-cold.html

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Ford F150 Ac only blows through defrost vents?

http://technoanswers.blogspot.com/2012/01/forf-f150-ac-only-blows-through-defrost.html

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Dodge A/C come out of defrost vents only?

http://technoanswers.blogspot.com/2012/01/dodge-ac-come-out-of-defrost-vents-only.html

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Ac vacuum line on dodge cummins?

http://technoanswers.blogspot.com/2012/01/ac-vacuum-line-on-dodge-cummins.html

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Ford ranger AC blows cold through defrost vents instead on cabin vents?

http://technoanswers.blogspot.com/2012/01/ford-ranger-ac-blows-cold-through.html

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2005 Chrysler PT Cruiser: A/C Blows Warm?

http://whoisbyme.blogspot.in/2012/06/2005-chrysler-p8t-cruiser-ac-blows-warm.html

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2009 Mercury Grand Marquis: A/C blows Cold From Defrost Vent Only?

http://whoisbyme.blogspot.in/2012/06/2009-mercury-grand-marquis-ac-blows.html

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AC not blowing through Vents on 2007 Chevy Trailblazer?

http://schematicsdiagram.blogspot.in/2012/04/ac-not-blowing-through-vents-on-2007.html

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Passenger side temperature is warm air out of dash vents?

http://schematicsdiagram.blogspot.in/2012/04/passenger-side-temperature-is-warm-air.html

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These will help.

Thanks.

The blend doors are controlled by small electric motors.
One of the motors could have failed, or the blend door is sticking.

here ya go,don't ever let anyone tell you that they CAN'T get something.

http://images.gtcarlot.com/customgallery/engine/40960853.jpg ford f250 4 6 v8 vacuum hose diagram Bing images

I would suspect either the fan motor or the switch. But you should also check to make sure the fuse has not blown.

have you checked the vacuum lines underneath the hood? these lines become all worn and break up with all the heat over time. if the problem is that the air is blowing through the top of the dashboard (defroster), then start by checking the vacuum lines and replace them, they are an inexpensive way to start. hope this helped...

check the vacuum lines in the selector switch. the baffles that switch from hot air and cool air are vacuum controlled and if the lines are detached or cracked the suction will not move the baffles.

Their is a vacuum actuated valve that redirects the flow of air from the panel to the defrost vents when the defrost is selected. I would check the vacuum line running to the valve while the vehicle is running with the defroster on and check whether or not the line is pulling a vacuum to actuate the valve, if not you obviously have a bad line or vacuum line fitting. If you have suction on the vacuum you will need to check the valve and see that is functioning properly. The valve is usually located under the dash on the passengers side. If you are mechanically inclined i would go to a local auto part store and pick up a repair manual for your car for about $20 as they contain diagrams and info that will save you alot of money.

GGBMDB