Air conditioner

That would most likely be a failed mode control actuator or mode cam on the HVAC unit (images 1 and 2). To get to it requires you remove the hood release cable, the drivers knee bolster and then the lower left dash insulator panel (images 3 and 4). With those out of the way you can access the communications module and its bracket (image 5). Gently move it enough that you can see the actuator and the cam. Start the engine and move the control from feet-dash-defrost and see which parts move or do not to determine if the cam fell apart (common for the plastic to flex and disconnect) or if the actuator is bad. If it is the actuator and you have small hands you may be able to remove it at this point but most folks cannot. So remove the negative battery cable and then disconnect the communications module and remove it and its bracket. Now you can easily remove the mode actuator. Replace it and reverse the process. You can reconnect the communications module and the battery and start the engine. Wait forty five seconds and the system should re-calibrate the actuators and you can test it to be sure it now operates properly. Let it run for a few minutes, shut it off and reassemble it.