No heat just warm air

What have you checked so far ?
Radiator full of coolant ? Heater hoses getting hot ?

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 TEMPERATURE BLEND DOOR STUCK OR BLEND DOOR ACTUATOR MOTOR FAULTY,YOU NEED TO DO A EATC DIAGNOSTIC TEST TO GET FAULT CODE SEE WHY YOU ARE NOT GETTING HEAT.TO DO A DIAGNOSTIC TEST FIRST WARM ENGINE UNTIL IT GET 120 DEGREES.WITH ENGINE OFF IGNITION SWITCH ON SIMULTANEOUSLY PRESS OFF AND FLOOR BUTTON THEN WITHIN 2 SECONDS PRESS AUTOMATIC BUTTON SELF TEST TAKE UP 20 SECONDS INDICATING BY BLANK DISPLAY WINDOW ON THE EATC MODULE. IF DISPLAY IS BLANK FOR MORE THAN 20 SECONDS OR IF CODE 888 IS DISPLAYED GO TO EATC SYSTEM TEST UNDER TESTING IF NO CODES ARE DISPLAYED AND SYSTEM IS NOT OPERATING PROPERLY GO TO SYMPTOM DIAGNOSIS IF CODES DISPLAY RECORD CODES. BEFORE TURNING IGNITION OFF EXIT SELF DIAGNOSTIC.BY PRESSING DEFROST BUTTON EXIT THE SELF DIAGNOSTIC PRESS BLUE BUTTON. IF ALL FAIL LET A GARAGE CHECK IT OUT.BUT ALSO CHECK COOLANT SYSTEM IF COOLANT SYSTEM VERY LOW YOU HAVE NO HEAT PROBLEMS.

There's a lot of this going around! The first check you should make is the coolant level. If coolant is low, then it can't reach the heater core to provide heat to your cab.

Check the hoses to the heater core and make sure they aren't deteriorated. Also, it might be worthwhile to clean and flush the cooling system.

It's possible there is a problem in the controls for the air conditioning system, too. The various valves in the ducts are vacuum controlled, and if a leak develops, it's possible that cold air is being mixed with the heated air.

first check and see if it has a thermstat installed or stuck open, second, make sure that your heater has not been bypassed by connecting the two hoses together

3 words come to Mind. Heater Blend Door

the blendor actuators strip out the gear inside the actuator cases on these all the time. replace the actuator.

your problem is caused by the air temperature control blend door actuator motor being defective, the little motor moves the door that gives either hot air or cold air or a blend of the 2.