Christmas Tree Lights Troubleshooting & Repair Guide
By 
If 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.
What causes an entire section of a string of three wired lights to go out? I have some that half or a third of the string are out. They failed bulbs are always toward the end of the string and continuous.
Hi Don,
Have you checked the fuse inside of the plug to make sure that it is not blown?
If the fuse inside of the plug end is bad the lights will not work,
Let me know if you need more help.
Happy Holidays!
Joseph
the hole strand don’t go out just the ones that got real bright
I have a pre-lit Christmas tree. One of the strands had a few bulbs shining very brightâ€â€brighter than all the others. Next thing I know, they went out. One half of the strand of lights is burned out, and the other half of the same line are fine. I have replaced the fuses with 2 different sets and still no luck. Any ideas what I can do to fix them? All the bulbs that are out are dark like they literally burned out. Please disregard the first comment. I need help with this one (with the correct email address.)
Hi Dan,
This actually happened to me on my pre-lite tree. I wasted many hours and then though to myself, Why don’t I just go out to Walmart and buy a few new strands of lights and then replace the whole strand. On my tree, like many trees there are little green c-clips that you can just clip off and then remove the pre-existing light string. Last year I changed out two strands.
This year I took all the old strands of the tree before I put it together and just replaced all the strands to save myself the headache of more strands going bad mid season.
It took me about 3- 4 hours to replace all the lights on a 7.5 tree and tool 1100 lights which was 11 boxes of 100 lights from Walmart @ $1.98 each.
If you have any other questions or need more help let me know,
Merry Christmas!!
Joseph
Thanks for your reply Joseph. I’m amazed someone actually responded, and so quickly. My tree is also from Walmart, a Holiday Time Prescot Pine #14 all white lights. Did you use 100 bulb strands of light or 50 bulb count? Before I take the time to restringing those lights, it would be nice to know if I am using the right length. Thanks again.
Hey Dan,
I used 100 count colored lights even though my tree had white lights originally. You could off course use white or colored, I just missed the colored after having the white for a few years. If I was to do it again, I would recommend using a larger sized strand like 500 count if possible. I remember seeing something like that at Walmart when I was there the first time, 100 count lights work fine its just you wind up with more plugs etc, then again, if a strand goes bad replacing the 100 count would be better, so I take that back, use a 100 count stand set either colored or white and then just remove those little green c-clips and then install the new lights.
When I installed my new lights I just put them on the branches and left the c-clips off like the old days with the real trees. Call me old fashioned but I like to put the lights on and off each year with the kids and the wife ;-)
If you need anything else or have more questions let me know, and of course stop back and let me know how you made out!
Merry Christmas!
Joseph
BTW: We have like over 900+ articles you might find useful
http://wetheadmedia.com/all
Once again, If there is anything else let me know
Joseph,
Thanks once again. We have the white lights (my wife’s favorite) for now. But, I have our first 6″ apt. sized tree (not pre-lit) in the basement with the fun colored lights. The kids and I enjoy that one. Thanks again. Merry Christmas to you too.
I use walmart brand mini lights, usually 100 count strans. After a few days of use I am finding half of the set out with the bulbs all blackend, and burned out. I put up over 60,000 lights . This is the first year I have had this problem. I have been using the mini clear on the roof, this is where the problem has beed happening.
Hi Steve,
Were they indoor or ourdoor lights?
the boxes says indoor/ outdoor. tipical walmart mini light that sell for 2.50 per box. been using them for years. Almost looks like power surge to half the set.
I read your info above and was proud when I changed the fuse on my outdoor lights and VOILA, they worked again; for about 10 seconds and then they all went out again. I had checked them on an indoor outlet first, they worked, so I took them outside and plugged them into the end of the strand already out there when they only stayed lit for less than 10 seconds. Any suggestions?
Hi Rachael,
Thanks for the kids words about the article. If the fuse keeps blowing that could mean there is a short in the wire. Any chance you have a cat? Cats are known for chewing through the wires and causing a short.
If you do not have a cat or even if you do, you will either have to find the short in the light strand or replace the strand.
Let me know if you have any other questions or need more help!
Merry Christmas!!
Joseph
If you try to string too many sets end to end, the current draw will be too much on the end closest to where it plugs in and blow the fuse. sometime you have to run an extension cord to the middle of a long run like that to avoid blowing the fuses at the end.
I have three sets of lights connected together. All three turn on when plugged in. After about a half hour the first strand shuts off while the other two continue to work. ASfer about half an hour the first one lights back up. ANyone have any ideas why this is happening?
thanks
the plug on end of my string of lights has a fuse but in overheated and melted the fuse slide .so I couldn’t open it ,Is there someplace i can buy a new plug Ron
Hi Ron,
The local hardware store or maybe Home Depot Or Lowes.
Happy Holidays!
Joseph
Hi, Joseph… got a new pre-lit tree last year and found my Hallmark plug-in ornaments do not fit into the sockets of the tree’s light string. Looked for a new tree this year and finding the same thing — also with just the boxes of lights. Why have “they” changed the light sockets? This is not on LED — just the regular mini white lights. Many thanks!
Hi, Joseph. I have a 7.5′ Prescott Pine Pre lit tree from Wal-mart. It is probably 7 or 8 years old. For the first few years, I had no problems, then I started getting entire strands of lights burned out (the bulbs are black and not working). Every year for the past 3 years, I have replaced between 100 and 200 individual bulbs, and usually about half way through the season, I get more that are burned out. It’s hard to tell if they are the bulbs that I just replaced or not. Any ideas why this is happening? Am I better off replacing the strands like you sugggested above? Will I continue to have this problem until I do?
Thanks!
We have a prelit tree that we are assembling – 4 years old. On the bottom portion, two of the strands seem to be working and the other does not. All of the bulbs on the strand that was not working were black. We have replaced all of these bulbs as well as the fuses for all the plugs in this section. We have also tried using the Light Keeper Pro to find why the strand doesn’t work. We are at our wits end – replaced and looked at every bulb in that section (probably 100-150)…any suggestions??
We are trying to fix most of the strands on a prelit 3 year old christmas tree that have gone out. I bought a lightkeeper pro but my problem is that I cant seem to get ANY of the bulbs out of their socket. Using a screwdriver, fingernails, the bulb remover tool on the lightkeeper, nothing seems to be able to pry them out. They each have little flip tabs that I can open, but then the bulbs won’t pull out without breaking off their bases. Any ideas? Thanks!
I purchased a Home Accents Holiday 5pc spiral tree pathway light set from Home Depot 2 years ago. On the last tree of the 5 (furthest from the plug-in) a the entire tree is out. When I tried replacing with some bulbs from another light string ( I used up all the bullbs that came with the set and I am pulling the bulbs out of the plastic base and re-inserting the different bulbs in there) the bulbs are very dim. But the tree actually lights. Are there different size bulbs for these sets? Any help would be appreciated.
I have had this fake christmas tree for seven years and last year the light on the top portion of the tree, both colored and non-colored, didn’t work, this year it happened again. I was moving some of the wires around that the white lights went on for one of the sections but still not all of them. It there a way to get the colored and white lights on my tree to all light up without unscrewing every single? or do I have to live with a half lit up tree?
I have a string of lights on my tree that seem to have a faulty plug. I have it singled out and plugged into an extension cord alone. Depending on how I jiggle the plug, the lights will come on, but when I let go, they go out. Is the plug changeable…this string is at the top of my tree and burrows down to the extension cord so pulling it out will be time consuming and make me cuss too much for this holiday season. Any advice would be appreciated as long as it’s not just simply replace it, haha!!!
I have several 100 bulb strands of lights on which only half of the lights go on. They have a 3 strand wire. I checked and replaced the fuses. I can run another strand off the terminal end into which i can connect another strand of lights that will go on. Is there any way I can make them all light up?
Hi Joseph,
I have the usual string of lights where the first half or the second half of the lights are out. I assumed the fuse is the problem. I opened up the container and pulled out the fuses and examined both. It looks like the wire is intact in both. Do I then assume one is bad and replace both fuses?
Colin
of course lights in middle of tree are out, I just unplugged 3 strands from each other but nothing else went out, why not?when i plugged in the new strand it won’t come on.