Went to move my car which started fine this morning but the battery was now flat so i started it using my booster and left it running to charge the battery it was then i smelt burning and smoke started comming out of the drivers door card and when i touched the door lock i burnt my thumb ,it was just like touching a boiling kettle !!.I was starting to panic by this point and its the quickest i have removed a door card to unplug everything(yes i know now i should off disconected the battery but didnt think at the time). Ive found a black box on the inside of the door which was also red hot and smelt of burning it says heiz element on it so i presume its for heated door locks which i didnt know i had. Does it heat the mirrors as well,are they prone to buring out and should i replace it with new one or just not bother putting one back in ??