Everytime I turn the vents on in my car it only blows hot air no matter how low I set the temp. ?

BROKEN  HEATER controller maybe! DO you FEEL the cable move with the SWITCH. or the HEATER CONTROL VALVE or BOX  

turn the ac on then

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Thanks for sharing this little

There used to be a vacuum motor that controlled the plate inside the plenum and they rarely if ever failed. When they replaced them with a small electric motor that is controlled by the HVAC control module, problems arose. It's either of three things: first would be something like an ink pen fell down into the plenum (duct) and got wedged into the temp control plate, or, the tiny electric motor stopped working, or, the HVAC controls are bad which usually means replacing a expensive module but some can be repaired my replacing the switch or knob or lever mechanism that controls the electric motor inside the plenum or duct.

Did you push the AC button?  Yes?  Did it light  up?  Yes, something is wrong with the AC system in your car.  See a mechanic.

The blend door is no longer functioning, (not moving and stuck on the position that blows air over the heater core). The door is a gate to blend outside or air conditioned air to the vents that move between hot and cool air - well it used to move between hot and cold.

That's nice. Did you want to ask a question while you're here?

Well, if you set it on low you will get cold air... so now what is your question as non asked. 

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If you are not stupid as you say, check the Freon in the AC as it needs charged. A smart person would do that. A smart person would ask a question also, something you did not do.

Thanks for sharing this little tidbit of information.

Do you have a question you would like to ask while you're here?