Heater/AC not wanting to switch from hot to cold or Vise Versa.
 

Hello! I got a 2015 Mazda 3 sports trim with 55k miles on it. Recently I've been having troubles switching the climate control from hot to cold. It also will be stuck on warm a lot of the times even when on max AC.

When I try switching it from hot TO cold, I have to move the temp knob to COLD and and back to hot and back to cold with the fan speed below the 4th stage. Sometimes it doesnt work even then.

When I try to switch it to have hot air come out, I have to crank up the fan speed to max and turn it all the way off. And keep doing that until I hear a "POP" from inside my dash. Under my infotaintment system is what it sounds like but it's hard to tell because it happens on full fan speed. Then it will start blowing out hot air. If I turn the fan to a lower speed it will sometimes be stuck on the cold setting even when the heat is max in the climate control. This is super annoying and I'm about to move to LA within the next year so I don't want my heater on all the time....

Anyone know the part that would be causing it? I think it might be a vent that switches the airflow on the inside my dash due to the popping sound, BUT I can't find the part it would be called. I asked Mazda and of course they will charge $120 dollars to diagnose the problem... if anyone has any input I would be glad to hear it!!