How to Change a Fuse in Christmas Lights (And Keep It from Going Out)

Nothing’s more disappointing than plugging in your Christmas lights only to find that they don’t work. If your entire string of lights stops working, you likely have a burnt fuse. Luckily, replacing the fuse is quite simple and only takes a few minutes. We interviewed professional electrician Marvin Woo to teach you all the steps to replace a fuse on Christmas tree lights. Plus, learn how to tell if a fuse is blown, how to prevent blown fuses, and get answers to other common questions about Christmas light fuses.

Changing the Fuse in Christmas Lights: Quick Steps

Unplug your Christmas lights.
Find a male socket (with prongs) that has a compartment to hold a fuse.
Slide or pop the socket door open with a flathead screwdriver.
Gently pry the fuse out with your fingers or the screwdriver.
Replace any burnt, dark, or cloudy fuses with a new one.
Close the socket door and plug the lights back in to test them.

Section 1 of 4:

Replacing a Fuse on Christmas Tree Lights

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1
Unplug your Christmas lights. Always unplug anything electrical before you work on it so you don’t electrocute yourself. Find the socket that enters the wall, take a firm hold of the socket, and pull it out of the wall. Don’t pull the socket out from the cord, as this could damage your lights.^{[1]
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- Before unplugging, test your lights to verify that they are still not working. Turn on the switch to see if they light up.
- If all the lights on a strand suddenly stop working, it’s usually a strong indication that a fuse has blown.
- Woo suggests that you “first check the outlet the Christmas lights were plugged into to make sure there's power present.”^{[2]
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  Expert Source
  
  Marvin Woo
  Licensed Electrician
  
  Expert Interview. 1 December 2021.}
2
Find the male sockets and make sure they’re marked. Male sockets are those with metal prongs (plugs) as opposed to those that receive the plugs. Male sockets are the only ones that have fuses in Christmas tree lights, and they’re plugged into other light strands or into the wall. If a socket has a fuse, it will be marked with an arrow pointing away from the cord and a sliding door that conceals the fuse.^{[3]
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- Gather all the light strands that aren’t working, as you may have to replace multiple fuses.
- Make sure not to miss any male sockets that aren’t working properly. If a fuse is not working, the entire light strand will not work.
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3
Open the socket door to get to the fuses. Woo says the fuse is “usually right there in the plug end behind a cover that slides or flips open.”^{[4]
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Expert Source

Marvin Woo
Licensed Electrician

Expert Interview. 1 December 2021.} Some doors can be opened by pushing it with your finger, while others may require a small flathead screwdriver. If the door won’t come up by hand, use the screwdriver to gently pry it up. Don’t use too much pressure, as you don’t want to damage the socket or fuses underneath.^{[5]
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- Find the grooves on the socket door, which should be relatively obvious to your touch. You may be able to push it up with your fingernails, but don’t force it if it does not come up easily.
- A kitchen knife can also work if you don’t have a flathead screwdriver. Just be careful not to cut yourself.
4
Remove the fuses and examine them for damage. Most Christmas tree lights contain two fuses, but some may only have one. Carefully pop them out with your screwdriver and examine them for damage. Burnt fuses appear dark and/or cloudy and need to be replaced.^{[6]
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- The fuses should be located immediately behind the socket door. They are very small, so be careful not to lose them.
- The fuses should be easy to remove. Don’t use too much force or you could damage them.
- Some fuses may be burnt but do not show external signs. In this case, use a voltmeter to check their strength. If the voltmeter doesn’t register anything, the fuse is burnt and needs to be replaced.
5
Insert the new fuses. Most Christmas lights come with replacement fuses, so locate these if you still have them. Place the new fuses into the fuse socket. They should pop right into place, so don’t force them in. Make sure both fuses are secure in the grooves of the socket, then close the plug door.^{[7]
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- Usually, the spare fuses are in little plastic bags taped to the Christmas light set.
- If you no longer have the spare fuses, purchase new ones from an electronics store or online. Be aware it may be difficult to find the fuses at stores that do not specialize in Christmas lights or electrical repairs.
- If you used a screwdriver to open the socket door, you may need it to close it, as well.
6
Plug the lights back into the outlet. Woo says the next step is to “test your lights by plugging them into a working outlet.”^{[8]
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Marvin Woo
Licensed Electrician

Expert Interview. 1 December 2021.} If the fuse was the issue, they should light up. If the lights still do not work, there may be another issue rather than burnt fuses.
- Make sure the socket door is securely closed. You don’t want your fuses to fall out of place.
- If the lights still don’t work, check your cords for any fraying, verify that all the bulbs are secured and working, and make sure your socket is in good shape.

Section 2 of 4:

How to Tell if a Christmas Light Fuse is Blown

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Take the fuse out of the socket and examine it closely. In most cases, simply looking at the fuse will be enough to tell if it’s burnt. Burnt fuses typically have dark staining that looks like a burn mark. This is one of the strongest indications that a fuse will no longer work.^{[9]
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If there are no visible marks on the fuse, it could still be blown. An intact filament will look like a thin, continuous wire running from the metal cap on one side of the fuse to the metal cap on the other side. If the filament appears broken or you can’t see it, the fuse needs to be replaced.^{[10]
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If you can’t determine if the fuse is blown just by looking at it, use an electrical continuity tester or the ohm setting on a multimeter to test the voltage. If the continuity test is negative or the ohm reading is infinite, the fuse is unusable and should be replaced.^{[11]
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EXPERT TIP

Marvin Woo
Licensed Electrician
Marvin Woo is a licensed electrician and the Owner of Woo's Electrical & Appliance based in East O’ahu. With over two decades of experience, he specializes in troubleshooting issues and maintaining residential electrical systems. Marvin is both licensed and insured to complete electrical work in the state of Hawaii.

Marvin Woo
Licensed Electrician

Test the fuse’s voltage to see if it’s blown. Test the fuse for continuity using the continuity or resistance test on a multimeter. If the meter reads open, then the fuse is blown and should be replaced. If the fuse reads closed, then you may have a different problem.

Section 3 of 4:

Preventing Blown Fuses

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1
Make sure your lights are in good, undamaged condition. Before installing your lights, examine the strands closely to check for damage. Look for frayed wires and loose bulbs, and replace any strands with extensive damage. If the lights are 10-years-old or older, it’s probably time to replace them.^{[12]
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- Make sure your lights are designed for the area you intend to use them. For example, if the lights are made for indoor use, don’t use them outdoors, as they aren’t designed to withstand water damage and harsh weather conditions.^{[13]
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- When you’re done with your lights for the season, store them properly to prevent damage. Try wrapping them around a piece of cardboard or even around a Pringles can.
2
Don’t over-plug your outlets. If you plug all of your light strands into one outlet, the outlet could overheat and cause the fuses to blow. Use multiple outlets, and check your lights’ wattage and your home’s amperage to determine how many strands you can safely plug into one outlet.^{[14]
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- Your home’s amperage can usually be found printed near your main circuit breaker.
- Limit the amount of extension cords you use, as well, for the same reasons.
If you’ve been using incandescent lights, consider switching to low-voltage LED lights instead. LED bulbs require less energy, reduce the risk of blowing a fuse, and shine brighter.^{[15]
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Official site for the U.S. Department of Energy, which provides resources related to energy safety, conservation, and efficiency

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Section 4 of 4:

Christmas Light Fuse FAQs

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Long strands of Christmas lights often contain more than one circuit. If only half of the strand isn’t working, there’s probably something wrong with that circuit, like a burned-out or loose bulb. Check the strand and replace any loose or damaged bulbs to see if that fixes the problem.^{[16]
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In most cases, fixing Christmas lights is a simple task that can save you time, money, and the hassle of having to buy more. If the lights are already hanging or on the tree, though, removing and replacing them can sometimes be more time-consuming than it’s worth. It’s ultimately up to you to determine if it’s worth it.
Replacing the fuse in LED string lights works the same way as replacing the fuse in other Christmas lights. Unplug the lights, open the fuse door on the male socket, remove the old fuse, and replace it with a new one.^{[17]
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Christmas light fuses are relatively easy to replace, so it isn’t usually necessary to hire a professional. Just don’t work on exterior lights if the weather is wet, icy, or otherwise dangerous. If you have a large outdoor light display and don’t want to spend a lot of time repairing them, consider hiring local Christmas light installers instead. Additionally, if you’re dealing with exposed wires, leave it to the professionals to be safe.^{[18]
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How can you tell if a fuse is blown in Christmas lights?

Marvin Woo
Licensed Electrician
Marvin Woo is a licensed electrician and the Owner of Woo's Electrical & Appliance based in East O’ahu. With over two decades of experience, he specializes in troubleshooting issues and maintaining residential electrical systems. Marvin is both licensed and insured to complete electrical work in the state of Hawaii.

Marvin Woo

Licensed Electrician

Expert Answer

Start by checking the outlet that the Christmas lights were plugged into to make sure there's power present. If the outlet isn't the issue, use a multimeter to test the fuse for continuity. If the meter reads open, you can know for sure that the fuse is blown and should be replaced.

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My plug receptacle doesn't show an open door. How do I get to the fuses?

Community Answer

Then the product most likely does not have a replaceable fuse. Not all products have this feature. However, do look carefully, because some products use only a single fuse, and the door may be smaller.

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My fuse is stuck in the upper part of the light plug. What do I do?

Community Answer

Try using a pair of pliers to straighten out one or two bends in a paper clip, then create a short (~1/16th inch) hook, bent to about 90° at the end. Work it into the fuse recess until you can hook the far end of the fuse and pull it downward and outward. This won't be as smooth as it sounds, but persistence will eventually pay off. Try not to break the glass in the fuse. But if you do, it will probably make things easier. Just be sure to get all of the old fuse (including the second metal cap and the small pieces of glass) out before inserting a new fuse. It may take a magnifying glass, but one of the metal caps should have the fuse's rating (Voltage and Amps) stamped into it.

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Tips

If you remove your replacement fuses from your Christmas lights, put them in a safe location to ensure you won’t lose them. You never know when you might need them!

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Warnings

Always unplug your Christmas lights—or any lights—before attempting to replace the fuse or do any kind of electrical work.

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