Plumbing, Heating and Pool Repair Guides

Christmas Tree Lights Troubleshooting & Repair Guide


WeT HeaD KnowledgeIf you have a set of Christmas Tree Lights that are giving you problems and not working you will have to do something called troubleshooting. Most sets of Christmas lights can be repaired easily, but sometimes it will be just better to replace the strand of lights. There are also two different types of Christmas Tree Lights, you will have two strand and three strand wires. The lights with the two strand wires will all go out when one bulb goes bad compared to the lights with the three strand wire.

Most of the time the fuse or one of the bulbs has gone bad causing your set of lights to partially work or even not work at all. Replacement Christmas light bulbs and fuses will usually be included with the packaging when you bought them. Most of the time there will be a small clear plastic bag that is taped to the end of the light string near the plug and inside this bag you will find a few extra fuses and bulbs. Some brands will also include a flasher bulb so you can have your lights flash.

How To Replace The Christmas Tree Light Plug Fuse

On the plug of your lights you will have a fuse that will protect the circuit if it overloads or there is a power surge. Each brand of Christmas lights is different but most of the time you will have to use a small screwdriver and pop out a little tab. Once you pop the tab open on the plug that is on the end of the light string you will be able to remove the fuse. The fuse will just fall out if you turn the plug upside down so that the fuse opening is facing towards the ground.

Once you have removed the old fuse you will want to take your new fuse/s and slide them into the opening. Now that the new fuses are in place you will want to shut the tab on the plug. If you have replaced the fuse on your light string and your lights still are not working you may want to make sure the outlet you have them plugged into has power. You can test this by plugging in a string of lights that you know work.

How To Replace Bad Christmas Light Bulbs

When you have found out what bulb/s are bad in your string of Christmas lights or Pre Lit Tree you will now need to replace the bulb. The first thing you will need to do is to make sure that the lights are unplugged from the electrical outlet to make sure you do not get shocked. Once you are certain they have been unplugged you can remove the light bulb from the strand using a Christmas Light Bulb Puller or you can gently pull on the light bulb base and slowly wiggle it out. If you have a small Flathead screwdriver you can also take it and catch the edge of the plastic that holds the bulb into place and gentle pry it out.

Once you have removed the bulb/s that are bad you can either insert a flasher bulb in its place to make you lights blink or you can insert a new colored or white bulb depending on what will match your light string. To make sure that you are installing the new bulb correctly you will want to make sure that the two wires on the side of the plastic bulb casing are aligned with the metal inside of the light bulb socket. This will ensure that your bulb makes a good connection with the light socket so the bulb will light up when the strand has power. When you have all of replacement bulbs in place you can now test the strand of Christmas Tree Lights by plugging them back into the power source. If after you plug them in they still don’t work you should check your fuse and se if you missed a bulb. On three strand light sets the other lights should be lit and then just he bubs that are bad will not be lit making it way easier to identify which ones you will have to replace. 

How To Make Your Christmas Lights Flash

If you have a set of multi-colored or white lights and they do not blink or flash you can replace one of the bulbs with a flasher bulb. Most Christmas Trees and light sets come with a flasher bulb that can be inserted into any one of the bulb sockets and then the strand will blink. You can identify a flasher bulb because they will be clear with a small dab of red paint towards the tip of he bulb. You will fist have to unplug the string of lights from the outlet. Once the lights are unplugged you can pull out one of the bulbs and then insert the flasher bulb. Once you have replaced the bulb with the flasher you can plug the lights back in and in a few minutes the lights should begin to flash. If you want the lights to flash more you could also add a second flasher bulb in the strand.

How To Use A Christmas Light Bulb Tester

If you have no idea if your lights are bad or not you can use something they sell call a Christmas Tree Light Bulb Tester which is basically a plastic mold with a 9V battery inside. On top of this small tester will be a spot where you stick in the light bulb that you think is bad. If the light bulb is bad the bulb will not light up. If the bulb is still good you will see it light up because inside of the bulb tester is the 9V battery that will provide the power to do so. Christmas light bulb testers are a cost effective way to find and replace all the bad lights in your strand and will save you lots of time as well.


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  2. I hope someone is st ill monitoring this page. When I got my tree out of storage this year none of the 7 strings on it are working. They aren’t hooked in a series, all of them run back to wall plug where you stack them together. I have tried plugging them in one at a time, changing fuses and etc. I have bought new lights and strung them up which they work fine. I’m just perplexed has to how all 7 can go out at once when they aren’t connected together. I don’t know the model or name brand of the tree, bought if from QVC several years ago

    thx for any help

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