Things You'll Need
Christmas light string
Christmas lights use thin, light wires that can be torn easily through repeated wear or a sudden jolt. If this happens, it can cause the lights to flicker or to not work at all, and can pose a safety hazard. Fortunately, Christmas lights are simple devices; most problems can be solved by simply patching a single wire.
Unplug the Christmas lights. Always unplug electrical wiring before fixing it.
Assess the damage. Is the wire torn, or is it just the plastic coating that is torn? If it is only the coating, wrap the damaged part in electrical tape and skip the rest of the steps.
Strip the plastic coating away from the spot where the wire is torn. Cut a vertical slit in the coating with a craft knife and peel it back with your fingers.
Thread the broken strands of wire together so that at least an inch or two of the two pieces overlap. Then, twist the spot where the wires join with your fingers to tighten up the connection.
Solder the break. Hold a soldering iron against the wire at the break until it heats up. Touch electricians solder to the hot wire. Turn over the wire over and solder the other side to make a good, solid join.
Wrap all exposed wire and solder in electrical tape. Make sure the whole thing is completely covered.