Hot air from A/C

Hey, i went to Pep Boys to get my A/C checked due to hot air coming from the vents although I’m good on refrigerant. They did an evaluation and said that my compressor wasn’t coming on and that i needed to go to the dealer and get a replacement “Heater control head unit” due to short. I have an aftermarket radio installed so I’m really confused on what this is.

Is this located on the aftermarket radio or located inside the vehicle ?

I got a 2003 Honda Accord LX sedan. The pictures below are of the aftermarket radio