heat blend door stuck on a/c setting

It sounds like your blender door is stuck or the motor is broken you may need to diagnose the A/C door blender actuator.

My door actuator is also broken. You can spend hundreds to fix or you can do what I do, manually change it to hot during the winter and when you want it cool, you can use the switch. 1. Take the glove box door off by opening the door and pressing the two sides together. 2. Turn the heater switch to full blast. (You may "should" hear a clicking sound on the passenger side of the dash just under the glove box on the support column.) 3. Place your hand inside the left dash panel and try to feel for a lever, it will be located approximately 4-6 inches and to the left and down on the column. The lever is approx 3" long and you can push it in the up direction. This will now blow warm air. If you look under the drivers side dash board column you will see the approx position of this lever by viewing the actuator - it is usually white from the factory.