My rear vents blows hot and cold air ( back seats) but my front vent and defrost blow know air. When driving fast can feel some air coming out but when I stop it stops.

It's the vent actuator, it moves the baffle that changes the direction of the air flow.
Here is a video of a broken vacuum hose that creates the same problem.

It could also be a failed actuator.

2004 Chevy Tahoe. Hot air out of vents on driver's side, cool ...

answers.edmunds.com > Edmunds Answers

Jun 25, 2009 - Hot air from vents-driver side and cool air from vents on passenger side. ... The driver's side vents were blowing out hot air, and everything else wasblowing cold. ... you'll literally have to restart your tahoe/yukon at every traffic light to keep cold air coming ... I was also getting air only out of the defrost vents.

Hot air out front drivers side vents 05 escalade - YouTube

? 3:14
https://www.youtube.com/watch?v=5lnd8UNcx6M
Aug 3, 2013 - Uploaded by South FL Mud Club
Suddenly hot air started blowing out the air vents only on the drivers... ... is a very helpful video ,I wondering if this part number apply for my 04 chevy tahoe? .... I have cold air out of thepassenger side, but warmer air out of the driver's side. .... 2003 Tahoe No Rear Heat Fix, Suburban, Yukon XL Repair!

Heating and AC Temperature and Air Delivery Mode Door ...

repairpal.com > Problems > Chevrolet > Tahoe

Driver/passenger air vents blow hot then cold when using A/C. Back to cold when you restart the vehicle. Upvote (35) ... 2003 Chevrolet Tahoe ... I have a 02 Tahoe ,and the heat system is working only on the ceiling side of the car when turn.

2004 Chevrolet Tahoe Blows Hot Air - Sparky's Answers

With the car parked and engine idling, turn the ventilation control between windshield defroster and "open air ducts" to front and rear vents. Listen to pinpoint where the valves are that open and closes the air ducts. It sounds like the air duct to rear vents are blocked, and the cold air in rear air duct is coming from "outside ventilation." The air vent to allow hot air to the rear vent is stuck in "open ventilation" mode, like when you're driving in spring or summer months.

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.

Hard to read your question, do you mean it blows cold air out of the front vents and hot air out of the rear passenger vents?

If the air coming out of the front is just cool and not cold, and the rear vents are warm, you have low freon and need to have it serviced.

ck front vacc lines defrost vent is default sounds like no vacc on door

Hope I was avle to help, glad you up and going.

Hello according the the manual, the back vent are to blew cold air only..the fronts vents are suppose to the entire car...

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.