Note: We’re re-publishing this post (originally published Dec. 2, 2016 and written by Taylor Whitney) because, well, it’s about that time again, and this post is a perennially useful answer to a very common question. While you’re gearing up for the holidays, be sure to check out our latest Gift Guide and follow us on YouTube, Instagram, or Twitter to catch our holiday deals.
Sometime in the near future you’ll venture into your dusty attic or musty garage and pull out a miserably tangled set of Christmas lights. As sure as Rudolph’s nose is red, one of those light strings won’t light up (if you ever manage to get them untangled in the first place). Millions will throw out their broken Christmas lights and buy new ones, but you will not. You are a strong, independent person. You will save Christmas (lights) this year.
Thankfully, it’s not too hard to fix Christmas lights. And iFixit’s repair community has already compiled lots of tips and tricks for how to do it—which I’ll be summarizing here.
Before you start
Make sure the lights are completely unplugged from any electrical socket before you start your repair. (Or you’ll be the Christmas ham.) You also need to know which kind of Christmas lights you have: Incandescent Christmas lights or LED Christmas lights. Incandescent lights work via a current running through a filament, which is different from their LED cousins. (Try here for LED light solutions.) This guide is for incandescent Christmas lights, so make sure those are the ones you have!
Before you can repair Christmas lights, you’ll need to identify the problem with them first. There are lots of different ways lights can break. If the entire chain is non-functional, a blown fuse could be the culprit. If a section of the light string isn’t working, there might be a bad bulb or a bad connection between the bulb and the socket (like a corroded socket). If replacing the bulb doesn’t work, it might be a bad socket or broken wiring that needs to be removed.
Here are some common ways to troubleshoot incandescent Christmas lights:
The string of lights won’t light up
Possible culprit: A blown fuse
The fix: Pick up the pronged “male” plug at the end of the strand. There should be a small door on the plug. Slide the door marked “Open” in the direction pointed by the arrow. Remove the two fuses, and inspect them by looking at them up against a bright background (the sky works). If the fuse is good, you should see an unbroken strand of wire running between the two metal contacts. (You can also use a multimeter to test for continuity.) Replace all blown fuses with new ones. Small fuses are inexpensive and can be found at most hardware, home improvement, or big box retail stores. Make sure that you read the specs printed on the non-functioning fuse so you can purchase the correct replacement. Fuse extraction can sometimes be difficult, stay patient! Try removing them like you would a battery.
Tip: If you’re blowing fuses in your lights repeatedly, it is likely not the light strand itself that is at fault. Often linking too many strands of lights together can cause the fuse to give out. Try plugging the strand into a different outlet, preferable one that is on a different circuit.
Bulb won’t work or a section of the string won’t work
Possible culprit: A bad bulb.
The fix for small lights where the bulbs pull out: Gently grasp each bulb, and pull away from the socket. Once removed, inspect the bottom of the bulb and ensure that the two bulb copper leads are in their proper location (see picture below), and not twisted or missing. (You can also test bulbs for continuity with a multimeter.) Where you find a problem bulb, replace it with a new one. Continue with each non-functional bulb in the chain, up until you find the culprit(s).
The fix for large lights where the bulbs screw out: Gently unscrew each bulb and remove them from the socket. Replace the one you just removed with a new bulb and test the light strand. If the strand still has the issue, you can put the old bulb back in the socket and continue on down the line until you find the culprit(s).
String won’t light up—replacing a bulb doesn’t fix it
Possible culprit: Corroded socket
The fix: Over time, the contacts inside the socket can become corroded or filled with dirt and grime. This damage can prevent proper contact between the bulb and the socket, which often results in no power to the bulb. Use a small file or scratch brush to clean the wire contacts of the socket. Once the socket is clean, insert a new bulb into the socket.
I’ve tried everything and a bulb or section is still not working
Possible culprit: Bad socket or wiring around a single bulb.
The fix: If all else fails, the bulb socket may be broken beyond repair. Removing it isn’t too complicated though, and should restore functionality to the rest of your lights! There are two potential ways to you can approach this repair.
Using a wire connector: Use a wire cutter to remove the defective socket from the light strand. Strip about 1/2″ of insulation from both wires. Twist the wires together and insert them into a waterproof wire connector. Turn the connector several times until the cap feels secure, and you can tug on it without it falling off. If replacing the bad socket fixed the problem, consider putting in some silicone sealant into the cap in order to keep moisture out and prevent the wires from corroding.
Using weatherproof heat shrink tubing: Use a wire cutter to remove the defective socket from the light strand. Strip about 1/2″ of insulation from both wires. Solder the wires back together or make a western union splice. Then follow the instructions in our How to Use Heat Shrink Tubing guide to protect the wires.
Be sure to check out our step-by-step Christmas lights guide. And if you have any tips or tricks to add, be sure to tell us about them in the comments. Now, go forth and save Christmas!