Do Christmas lights have fuses?

Do Christmas Lights have fuses

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.