Defroster keeps switching or other options

Hey, I have a 05 Prius base model, I do have an aftermarket head unit in it and yes I did resister jump the 2 wires for the AC to work. About the last 2 weeks I've been having problems with my defroster, which I'm in California and I need the defrost on all the time to keep it from fogging up. I haven't done anything to my car in the last few weeks. What could cause this???? I have checked all my fuses and they are good. *Unless I'm missing some fuses* but everything was fine before, just started doing this.