Fix burned wire inside electrical boxes by replacing charred insulation. You can do this quickly and easily without pulling in new wires. So you're finally getting around to replacing the ceiling light fixture when you discover that the wiring insulation has turned to charcoal and. The discovery of burnt electrical wiring, often signaled by a smoky odor or visible charring, presents an immediate and serious hazard. These are designed to turn off the power to the sockets, lights, cooker and so on when there is an overload of current or a fault on the circuit. These problems create heat, sparks, or arcing that can ignite nearby combustible materials and lead to a fast-spreading fire.