For the brake lights, the way in which the bulbs are plugged is not perfect, and therefore, the bulb terminal and the socket terminal may rub against each other and produce abrasion powder, which could accumulate on the socket terminal and work as electrical resistance. If the heat produced by this causes the insulating plate for the socket terminal to melt, a short circuit may occur between the socket terminal and the pressure spring resulting in a blown fuse, in which case, the brake lights, the auxiliary brake light and the horn would fail.