Replace the fuse Most new packs of Christmas lights come with a replacement fuse—which should give you a clue as to how common fuse problems are with these things.

To fix burnt-out bulbs, untangle all string lights and check for frayed wires, damaged sockets, or broken bulbs. Discard any damaged bulbs, and then replace them with spare ones.

Lighting up Christmas: The quick fix for broken light sets The LightKeeper Pro, from Ulta-Lit Tree Company, is a tool that repairs most sets of malfunctioning miniature Christmas lights.

How to fix broken Christmas lights Don't waste a light strand or risk using a broken one. You can fix it.