Why does my Freightliner blast frigid air in the cab regardless of settings

When I turn on my opti idle it doesn't seem to matter how I have the temp set up front, it always comes out ice fucking cold. The bunk vents run reasonably warm but even if I turn the dial in the cab all the way to hot it blows cold as fuck. If I press the "A/C" button in the center of the temp dial it blinks once or twice and the blue light stays on. If I turn the vent fan all the way down, it (you guessed it) keeps blowing ice cold air full blast. Am I missing something?