We hear this question from folks who are puzzled that their lights worked fine last season but are half out when they pull them out of storage.
Or their lights suddenly half go out during installation.
What gives?
Incandescent Christmas tree lights (aka mini lights) are wired in series so if your lights go partially out you have one of three issues:
1. A light bulb has come out of its socket or is half out of its socket and it has brought down the circuit. For light strings that commonly have over 50 bulbs, they are constructed in 2 or more continuous circuits. If a bulb is missing in a circuit only the bulbs in series of it will go out. That’s how you can lose 1/2 or 1/3 or 1/4 of the string.
But don’t lights stay on if a bulb burns out?
Yes, as a general rule of thumb, a small wire at the base of each glass bulb will continue to conduct electricity if the filament “burns out” but if the bulb is actually out of its socket, the lights don’t actually stay on.
The solution: Visually inspect each bulb in the part of the Christmas light string that is out. Don’t take out and reinsert each bulb because that’s hard on fingers and will more than likely create larger problems. Check for any bulb that is missing or partially unseated from the socket and if you find a space or wonky bulb, replace the bulb with one of the two extra bulbs that hopefully were included with your light set or gently push the bulb back into its socket.
2. The rating of the light string was exceeded and the bulbs blew out the wire at the base of each bulb that is supposed to conduct electricity. This happens sometimes when the bulbs are “smoked”.
The solution: Check the rating of the light string and don’t plug in more lights than the manufacturer specifies. Visually check the part of the light string that is out and replace any smoked bulbs.
Note, if you’ve run way too many lights in series you may have permanently damaged your light sets. Purchasing new sets may be necessary if replacing bulbs don’t work for you.
3. There is an issue with the wiring harness and the copper wire is broken in the string. If all the bulbs are seated and none are smoked, more than likely there is an issue with the actually wiring of the Christmas light string.
Damage to the wiring can be caused by age, squirrels, pulling and tugging on the light strings during take-down at the end of Season.
If this is the problem with your light string, the best solution is to begin again with a new string of lights.
What if the entire string of lights goes out?
If the entire string of lights is out, the issue could be that it is on a single circuit and is due to one of the issues above or the fuse for the entire string might be out.
See our blog about the entire string doing down for more information and troubleshooting tips.
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I have two strings with these blank spaces that look like they could accommodate another bulb or maybe serve some sort of electrical function (resistor?).
Both strings don’t work starting right before this spot.
Any thoughts?
That’s a weird situation. I’m not sure what the manufacturer had in mind for that part of the light strings but it is odd that they don’t work starting right before that spot. Are they custom strings built for a specific tree or structure? They may be customized to specifically have that dark gap. They also might have a wiring issue due to a design feature that has created a break in the wiring at that point as the light set has been used. Without having my hands on the actual strings it is hard to picture exactly what is going on. You might reach out to the manufacturer to see what they intended for those spaces to determine your next steps.
Unfortunately, my half-out strand is attached to a pre-lit tree. The bottom section has 2 rows of branches, and the top row of the section (the end portion of the strand) is out. I have checked all the bulbs, wiggled them to make sure none are loose, even though they are the type with the little latch that clicks the base in place, so it would be difficult for that to be the problem. I have changed out any obviously blown bulbs. I have changed both fuses in the prong end, even though neither appeared blown. My light/circuit tester is not consistent with showing me exactly where the electrical current stops, so what do I do? Is there anything else I can do? I don’t really want to buy a whole new tree. This year, we just dealt with dark section, but I’d really like to fix it. The tree base is still sitting out halfway through January because I’ve been trying everything I can to fix it. I’ve read about 2 dozen internet articles. You guys seem like you must know your stuff, given your specific blog name. 🙂 Please help!
Hello!!
Sorry for our late reply to your great question. We have been in your exact situation and feel your pain. Glass lights have about 3000 hours of life and you may very well be at the end of your light string’s life span. You’ve described a process where you have really worked on troubleshooting and the remaining issues may be related to wiring and socket failure that happens over time. During the off-season, you might consider clipping and rewiring the tree with new light strings. I’d plug any new lights into each other and into their own splitter. Reinstalling the lights will extend the life of your tree. Without the pressing deadlines of Thanksgiving and Christmas, it is a tedious task that can be worked into a few evenings. Note the spacing of the light strings currently installed on the tree and try to replicate that when purchasing replacements.
Sorry that I don’t have a better answer but it sounds like you have fought the good fight and replacement is your next best option.
On one of my 150 mini bulb strands there are three with bases that are white instead of green, and the bulbs in them look a little different. I can remove them from the socket, but I can’t seem to get the bulb out of the base. What are these bulbs for, and should they be replaceable? Thanks.
Sorry we missed your comment, Bob, and it took us so long to reply. That is a puzzler. We’ve not seen a string of lights that has bases that are actually different than the rest of the string with different kinds of bulbs.
That sounds like some sort of custom light string. We have seen strings pre-installed on Christmas trees will sometimes have unexpected innovations like this. Since your bulbs can be removed, historically, that can indicate there are replacements available. Reach out to the manufacturer or for replacements or cannibalize a replacement bulb from one of your existing sets. Sometimes one set has to sacrifice for all the others. Hopes that helps a little.