How To Fix Christmas Lights: A Quick Guide to a Merry & Bright Holiday - Backyard Boss
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How To Fix Christmas Lights: A Quick Guide to a Merry & Bright Holiday

It’s every Christmas decorator’s worst nightmare. The tree is dressed with string lights, the ornaments are on, and all that is left is to plug it in. But as you inch toward the outlet, you realize that you didn’t test the lights before you put them on the tree. They’re buried beneath several layers of ornaments. Finally, you plug in the lights—and to your horror, half of them do not work.

It doesn’t have to be this way. Understanding how to fix Christmas lights is quite easy and can save you a huge headache when the holidays come. All it takes is a little bit of an investment with time and money. In our handy guide, we’ve compiled everything you need to know about what makes Christmas lights work and how to fix them when they don’t.

Why Do Christmas Lights All Go Out When One Bulb Blows?

When lightbulbs are attached to one another in a series, electricity runs directly from the power source to the initial light, and then continues to move from bulb to bulb until it is able to return to that power source. Through this kind of light setup, a burnt-out filament in one bulb will create a kind of open circuit. Electricity is not able to reach the bulbs behind the burnt-out bulb because the open circuit will stop it from moving forward. So, those lights are not damaged at all—the one burnt-out light is the one that must be fixed, and the rest of the lights will work once that happens.

woman hanging christmas lights on home exterior

How Do You Know Which Bulb is Out on the Christmas Lights?

This is incredibly easy to find out,and there are several ways to do so!

The easiest way to find the faulty bulb on a set of incandescent Christmas lights is to use a Christmas light tester. Simply put each light up to the tester, and the tester’s LED light will indicate that the bulb is functioning. Once you hit a bulb that gets no response, then you’ve found your damaged bulb. You can also use a non-contact voltage detector that will work virtually the same way.

    Klein Tools NCVT-2 Voltage Tester, Non-Contact

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    Voltage Tester automatically detects and indicates low voltage (12-48V AC) and standard voltage (48-1000V AC) allowing broad application. High intensity, bright green LED indicates the tester is operational.

If you don’t have a tester, you have some additional options. In many cases, a burnt-out lightbulb will appear much darker than functioning ones. A burnt bulb’s filament is broken and in some cases will detach and rattle around in the bulb. With a careful eye, it really isn’t. that hard to find the damaged bulb.

Do LED Christmas Lights Stay On If One Burns Out?

If one LED bulb goes out but isn’t significantly damaged, then the rest of the lights will likely work. However, if an LED bulb is crushed or cracked all the way to the core of the bulb, then half of the lights may go out. In some cases, the entire string will go out.

How to Fix a Strand of Christmas Lights

Check the Fuse

Even notice that your Christmas lights always come with those little plastic and metal tubes? They actually have a purpose! If you look at the underside of your Christmas light’s plug, there will be a little door that you slide open. Inside are the fuses for the light, and those little extra tubes are replacement fuses. When your lights stop working, replace those fuses first.

Check the Lights

closeup incandescent christmas light bulbsUsing a Christmas light tester, identify which bulb is burnt out. We recommend checking all of the lights, as string lights can have several burnt-out bulbs at once. If you identify a dead bulb, try tightening the base of the bulb. This could fix the problem immediately, but if your bulb is completely burnt out, it’ll need to be replaced.

Replace the Bulb

Once the burnt bulb is identified and you’ve made sure that it isn’t just loose, it’s time to replace it. Most sets come with a few replacement bulbs, so make sure you hang onto those little bags when you first buy your set! You can also buy replacement bulbs at most home improvement stores.

Delicately squeeze the bulb’s base to loosen and remove it. Find the two copper wires that sit inside the old bulb and make a mental note of their position. Once the bulb is removed, insert the new bulb. Those two copper wires need to be perfectly aligned with the holes in the base, so this will take some care. Once the bulb is inserted, twist it to ensure it is firmly in place. Test your lights to make sure the process worked.

Remove Broken Sockets

If your new bulb still isn’t working, your socket could be the cause.

Unplug your lights. Use wire cutters to cut the wire on both sides of the damaged socket. Use a wire stripper to pull off around half an inch of insulation from both cut ends. Then, twist the two wires together. Purchase a twist connector from your local hardware store and twist this over the wire to hold it in place. Then, test your connection. Your lights should be working fine!

a string of multicolor incandescent christmas lights on the rug

Store Your Christmas Lights Properly

Cheaper string lights aren’t very durable, and will likely break down by next Christmas if you don’t take good care of them. When the holidays are over, be gentle when pulling down your string lights. Before storing them, plug them in to ensure that they are still working. As a general rule of thumb, it’s a good idea to keep your Christmas light boxes and to store your lights in them when not in use. Balling up your lights and tossing them into a plastic box together could cause damage.


It’s crazy how easy fixing Christmas lights can actually be. Now Christmas decorating doesn’t have to be such a stressful hassle!

How was our guide to fixing Christmas lights? Tell us which technique worked for you in the comments!