My toyota sienna 2005 is "runnng hot" and I

Blend door has gone bad.

its a toyota. enough said

does the hot/cold control knob feel like it is moving something or is it very hard/easy to turn ? sounds as if the hot/cold setting is stuck at hot would need to strip back heater control panel and follow the control wire/cable to the heater box where a flap opens and shuts for hot or cold air and see what is happening ,cable may have broken , flap may have come off it's hinge won't know until you get a look at it , the engine isn't over heating is it ?

do you know if the heater core hoses are hot under the hood? have you checked the coolant level? you mat also have a blend door motor problem

you must listen when changing the temperature from cold to hot to see if you can hear the heater duct opening & closing,if not could be a vacuum hose is disconnected or broken,or the vacuum motor that moves the duct door has broken you might hear a hissing sound,or a cable has broken,I don't think it's a fuse ,because it's working when you turn it on,those are good possible causes I have given you have fun & I hope you have small hands,limited space acess

As per your problem mentioned.There are few solved help links to troubleshoot these problems.Go through the list and Click the link below:----
Air conditioner blows air but not cold air http://repairhelpcenter.blogspot.in/2012/07/air-conditioner-blows-air-but-not-cold.html

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Car overheats and Air blows hot at idle? http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.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---------- 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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2005 Chrysler PT Cruiser: A/C Blows Warm? http://whoisbyme.blogspot.in/2012/06/2005-chrysler-pt-cruiser-ac-blows-warm.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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These will help.
Thanks.

Check coolant level.

try turning the blower down, if you have the fan on full you will feel cooler air from time to time. as the thermostat only measures the ambient tempreture inside the car when this level is met then it will turn off the heat so it will only blow the air from the car which will feel cooler.
if the car is still cold suspect the tempreture control in the car maybe faulty or the water level in the system maybe low.

Possible that heatcore is going or hose from heater is leaking or falling off.
You can go to www.autozone.com and see a full free online repair manual for your van

Check the valve that controls coolant flow to the cabin