Thomas Edwin Worthy

I have a 2014 Ford Edge with dual temperature control. As it has started to turn a bit cooler, I attempted to adjust the temperature in the car. I discovered I can only blow cold air. This is the same for both the driver and passenger side. I have read that I most likely need to replace the actuator, but there appear to be 4 of them based upon the parts list form Ford. Does anyone have an idea as to which one I need to replace? Thanks!!!