How to Figure Out Which Bulb on a String of Light Is Out

Inspect the string of lights looking for dark bulbs or wires that are broken or corroded. If the wires look faulty, it's best to discard the string of lights. Replace any dark bulbs with a new bulb and test the string, as the light can appear darker when the bulb has burned out.

Test the fuse in the string of lights by removing the fuse from the base of the string of lights. If the fuse is blown, it's as simple as replacing it. Most strings of lights come with a replacement fuse and one or two replacement bulbs.

Check out each bulb with a quick and gentle tug to confirm none of the bulbs are loose. If you come across a loose bulb, gently push it back in place. Test the string of lights if you find any loose bulbs.

Start at one end of the string and work your way through it with the bulb tester, testing one bulb at a time. Though this may seem like the same thing as testing a single bulb at a time, it's less time-consuming and slightly less tedious.