Do Christmas lights have fuses?

December 6, 2018

My entire string of Christmas lights just went out!  What do I do?


Short answer:

Yes, most Christmas lights have fuses in the male plug end. If the entire string of Christmas lights has gone out, this is the first thing to check for troubleshooting.

Long answer:

Most of the time, there is a little door in the male plug of your lights – whether they are light strings that have two plugs – male and female – or a set of craft lights that only have a single male plug.

See this photo below of a mini Christmas light plug with the little door.

There are fuses behind that door!!  Note this plug has a 3 amp fuse so you’ll need a 3 Amp fuse with the same size as the fuse inside to make your repair. (Hopefully, there are a couple extra fuses still attached to your string of lights or safely stored away in an orgaized fashion!)


Use a small flat head screwdriver to open the little door.


Using a small screwdriver, gently pry out your fuses.


See the photo below of a good and a bad or blown fuse. The fuse on the left has been “smoked”.  Fuses are basically a little glass cylinders with contacts on each end and a thin conducting wire connecting or completing the circuit from end to end.  When the current exceeds the rating of the fuse, the wire inside burns and opens the circuit.  (Which means your lights are no longer receiving electricity and go off.)

Fuses are usually included with Christmas lights so keep them in a labeled bag ready for future use. As an alternative, fuses can be purchased at auto parts stores. Be sure to have your light string’s maximum current rating and one of the fuses to take to the store to make sure the new fuse purchase is a good fit both physically and electrically.


Look hard at your plug.  If you have only one set of contacts in your plug but two fuses, that means that the second fuse is a spare. Move it out of its holding spot and move it to take the blown fuse’s place between the contacts. In the photo below, the contact is that little gold metal piece that makes contact with the metal of the fuse.

Metal to metal contact is required to conduct electricity in this circuit.

Keep in mind that some plug ends require two fuses and the second is not a stored spare. Take a hard look and notice if contacts are present for both fuses or just one.

After replacing the burned out fuse(s), shut the little fuse door and test out your lights.

(Note, this plug only needs a single fuse.)


Some plugs have “odd” configurations.  This plug has two little tiny doors instead of just one and required that both fuses be changed out.


We’ve also seen plug ends with little round screw in doors located between the plug prongs. Using a small screwdriver, you “unscrew” the little door to replace the fuse.

Why did my fuse blow?

More than likely, too many sets were connected in series.  

You may need to unplug a few sets before you plug the repaired set back into the run of lights. (And you may have a few more fuses to check and replace. You’ll know soon enough.)

Check the maximum number of lights strings that can be connected in series rating either on the box it came in, on it’s webpage, or check the tag to see if the maximum number of strings is listed there.

If you are working with C7 or C9 glass bulbs, find out the rating of your plug — is it 5 amps?  10 amps?  Reduce the length of the run or the number of lights installed if they exceed the maximum current rating for the plug end fuse.

Hope this helps!!

(See more about how many sets you can connect in series here.)

For more discussion, see our video on fuses in Christmas lights.


And this video showing the little door which I forgot to do in the video above.



Shellie Gardner
Aside from throwing dinner parties that feature at least two kinds of cheese dip, Shellie's passions include travel, Mid-Century Modern furnishings and finding the perfect street taco. Has been known to snort laugh champagne.

14 thoughts on “Do Christmas lights have fuses?”

  1. We bought a pre-lit tree that we used last year for the first time with no issues. This year we put the tree up and within an hour of plugging it in, all the lights went out. I looked at the 5a fuse in the main plug for the tree and it was blown. Now every time we replace the fuse and plug it in the plug gets very hot and eventually blows. We have blown 4 fuses. What could have changed from last year that would cause this? The tree has a 3 year warranty but I’d like to know why it’s happening in case I get the run around when I try to make a warranty claim.


    1. Hi Steve,

      We can’t give out formal electrical advice but an issue like that might result from damage to the wiring harness. This might have happened when the tree was taken down and stored or reassembled.

      Troubleshooting suggestions would include plugging the light string in individually and examining them for physical damage to the wiring.

      Leave the tree unplugged until your issue is resolved with the manufacturer. (Call them right away.)

  2. I have three strings of LED lights in series. The first and third light up, but the middle one is dead throughout. Any thoughts on where the problem lies. I did test them all first and they all seemed to work separately, unless something broke while I was putting them up. Thanks!

    1. Hello,

      That sounds like an issue with the wiring harnesses of your light strings. It might be time to retire the middle string.

      If we had an easy fix for that, we’d love to share it. Sorry, we couldn’t be of more assistance.

  3. Hi, my led lights don’t seem to have accessible fuses. Theres no sliding door or small screws to open a door, aound the male & female end of the plug the plastic looks totally sealed. Are there lights that dont have accessible fuses? But when I bought the lights in the little bag with the spare bulbs there is an extra fuse so I’m confused as how I would ever be able to change it.

    Thank you

    1. Hello Rosalie,

      That’s a great question.

      Some plugs have a tiny “door” that looks like a screw between the prongs of the plug. Take a look and see if that’s how your set is configured. You just unscrew the fuse holder with a small flathead screwdriver.

      Let me know if that answers your question. I wish that were more straightforward for you.


  4. Is there anything I can do increase the maximum of String lights that can be attached? I honestly didn’t know… and now I don’t want to remove all the lights I’ve put into my tree I’ve already lost so many needles in the process of putting them on.

    1. That’s a great question. You can reorganize how your lights are connected to power by using splitters and possibly extra extension cords so that the maximum run specification is not exceeded for your light strings.

      Without being onsite it is hard to give you direct advice on exactly how to change your electrical installation. Since you have put in the effort in to install your lights, please consider contacting a local electrician to assist you for a short omount of time to sort out your electrical configuration.

      (You have to make sure you don’t exceed your breaker specifications as well.)


  5. question….on my string of lights, 1/2 lite up and the other 1/2 are dead. what do I do to repair?

    1. Since only half the string is out, we know it’s more than likely not the fuse.

      More than likely the issue is one of two things:

      1. Take a look at the string and check to see if any of the bulbs have come out or are halfway out of the socket. Fill in any empty sockets with a replacement bulb or press any bulbs back in place. While you are looking for empty sockets, look to see if there are any lights that have “blown”. Replace those as well. If you see several bulbs that are blackened then retire the string.

      2. The other alternative is that the wiring harness has been damaged either when they were removed last year or something happened in storage. (Heat, damage to wiring, etc.) If this is the problem, then I’m afraid it would be time to retire the string.

      Hopefully, this gives you a place to start.

  6. GREAT article! I have a question. I’m trying to replace 2 broken plugs that are “fused” that are labeled “use only 3A max 125V fuse”. I can’t find them anywhere. Can anyone tell me how to find these as my wife LOVES the units they are attached to.


    1. That’s a tricky repair. Series wired light sets are low current and replacing/splicing in new plugs can affect their electrical specifications.

      Best to consult with a master electrician.

      1. Hey there, I have a light set that works fine on its own when plugged into an outlet but won’t work when plugged into another strand… however, I’ve used these for a few years and never had issues. Fuses seem good on all sets. Any thoughts?

        1. Hello Justin,

          That’s a tricky issue. It could be the female end plug of the string you are plugging into is the issue. Have you tried plugging it into another string to see what happens? The issue might be with the set you are plugging into instead of the set that won’t light.

          If you see the same issue plugged into a different string, it might be time to retire the strand that is currently uncooperative. (If it works plugged into an outlet but not when plugged into another set, it more than likely is not the fuse.)

          It is hard to say why this is happening to you definitively but taking lights down, wrapping, storing, and pulling them out again can sometimes cause small amounts of damage to the wiring resulting in issues like this.

          Sorry, I don’t have an exact answer but I hope this helps. Best of luck sorting it all out. Please don’t take chances with a wonky light string.

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