Ever since I tried to change the radio in my car the ac stays constantly blowing out hot air. I have checked the fuses and none are blown and the ac belt works and it has plenty of Frion in it. What else could it be?

 

Did you check and make sure that you got the wire harness plugs pushed in all the way on the back of the heater controls?

 

As far as I know yes, I unplugged it and plugged in back in.

 

Do you have the auto climate control system, the one where you have a digital temperature display?

If do, there is a built in self diagnostic you can run. It is in the HA (heating & air conditioning) section of the service manual. It starts on page 37.

click here for Nissan Service Manual Section HA