My air conditioner is blowing cold but it circulates from defrost to max

What is your question?

When you turn the a/c on, the whole panel lights up or it may not light up at all, it will be blowing on your face one second and then switches to defrost and in another second switch again. You can press the button and it will go back for a second but then on it own, switches again. I am pretty sure that the guy we bought the car from installed a non factory radio in this car but don't know if that has anything to do with it. Really need to fix this problem because my son can't keep the windows clear which is dangerous