Airceo13

ok, my heater is running really weird, when i turn it on half way it fades in and out, and my volt meter goes from 12v down to almost 6v... i have no idea what the problem is, i know its not that big right now, but it might get worse so better to fix it before it causes more problems. i just started doing it like 2 days ago.. another problem is that my deck just stopped working when i started my car... no power cant turn it on or anything... could it be possible that its a blown fuse? need some help guys thanks