All the outdoor Christmas lights are broken?
November 16, 2020 11:15 AM   Subscribe

This is a question I don't even want to try to google. Of 8 strands of outdoor LED Christmas lights, only one half of one of the strands will light up. First, how and why? I believe they are only 3 years old and they were working last year. Second, do I try to fix them, or just buy new ones?

If it matters, they are the icicle strand-type.
posted by kitcat to Grab Bag (8 answers total) 1 user marked this as a favorite
 
For each half-strand that doesn't light up, that means there is at least one burnt-out bulb in that strand.

Christmas lights are wired in series, meaning that if the circuit is broken by one light burning out, the entire strand goes out. Sometimes they are wired so that each half of the strand is on a different circuit, so that only half the strand goes off if a light burns out.

If you can get a spare working bulb, you can test the bulb in each location on the strand until the strand turns back on. That's one possible solution.

Another possible solution: Many light strands have a "shunt" for each bulb which is supposed to repair the circuit if the bulb burns out, and keep the entire strand from going dark. However these shunts are cheap and often don't trigger when they're supposed to. I've actually had decent luck using one of these types of devices (not endorsing that one in particular) to trigger the shunts and light a broken string of lights back up. It feels like a scam but it has absolutely worked for me in the past. It doesn't work 100% of the time but it has worked more than half the time for me.
posted by mekily at 11:29 AM on November 16 [1 favorite]


Are the strands plugged into each other in sequence? If so, separate each strand. and test them individually. Now, if you have a multi-meter it's pretty easy to check for issues with the fuses and plugs--here's a short video on how to do it, and there are many others if this guy (or his cluttered living space) aren't your cup of tea. Both of those problems are pretty easy to fix; if the issue is burned out bulbs, that takes a lot more effort and probably isn't worth it. As to the cause, water exposure causing rust when outside and mice chewing on the tasty wire insulatiion during storage are the two that come to mind.
posted by carmicha at 11:30 AM on November 16 [2 favorites]


A loose or broken bulb in the circuit can break the connection for the remaining lights in that strand.

Start with the first unlit bulb, wiggle each bulb as you work your way down to check for looseness and that it's tightly seated. If some of the lights flash on when you're doing this, check that bulb that triggered the flash - the connections are clean, unbent, tight. It may be time to replace the bulb.

If it doesn't work, then you want to go and replace each one with fresh bulb until you identify the bad bulb.

Second, do I try to fix them, or just buy new ones?

Fixing them is easy, if a bit tedious. Fixing also avoids contributing to landfills.
posted by Karaage at 11:31 AM on November 16


I do have a multimeter that I need to learn to use, so thanks for the video!

Additional question:

Let's assume that mekily is right about each half strand being on a different circuit. Do I understand correctly that if one bulb in that circuit is broken, then the lights on that circuit (that half of the strand) will not light? This tells me that in the 7 strands that do NOT light up it must be a bulb in the first half of the strand that's broken.

TL;DR So...what if two bulbs are broken, or three, or more? Wouldn't I have to replace pretty much every light in that half of the strand to get it working again?
posted by kitcat at 11:45 AM on November 16


Yep, fixable but tedious. Probably rusted/corroded/broken contacts for the light bulbs, which makes them appear burnt out. Too many in a section and the section doesn't work. In my experience, 3 or 4 bad bulbs is about where the whole section goes out. Each section is usually 50 bulbs, so a 100 bulb set will have 2 sections, but a 150 bulb set will have 3 sections, etc. Each section is completely independent (wired in parallel), so you can have a string with the first section out and the second section working.

Additional tricks:
If you're lucky, you may have a situation where you have just one too many burnt out. Sometimes if you take them to a completely dark room, the non-bad bulbs still glow a tiny bit, and you can identify the bad (dark) bulbs to replace.

If you have a working string of the same design, you can remove a bulb from a dead section and check that it's good by temporarily plugging it into a good string, then putting it back if it's good. Work through the entire bad section bulb-by-bulb until you identify and replace enough dead bulbs that the section lights up. Replace any additional dead bulbs you can now see. You'll probably have more dead bulbs than you have spares, so you will probably need to make one of the strings the sacrificial donor to give up its bulbs as spares.

My mom has a whole batch of icicles that must have been manufactured with a defect, so this is an annual event. The only way this gets simpler is to go through at the end of the season (and during the season, if accessible) and replace all the dead bulbs, so that one more bad bulb won't kill the section.
posted by yuwtze at 11:56 AM on November 16


Let's assume that mekily is right about each half strand being on a different circuit. Do I understand correctly that if one bulb in that circuit is broken, then the lights on that circuit (that half of the strand) will not light? This tells me that in the 7 strands that do NOT light up it must be a bulb in the first half of the strand that's broken.

Almost. If the two halves of the strand are on separate circuits, and the entire strand doesn't light, that means there is at least one bulb on each half of the strand that is burnt out.

TL;DR So...what if two bulbs are broken, or three, or more? Wouldn't I have to replace pretty much every light in that half of the strand to get it working again?

Yeah, this is the problem, that you don't actually know how many bulbs are burnt out... so even if you go through and put a new bulb in one socket at a time, there might be a second burnt out bulb. So it's tedious.

I will say that the advantage of the device I linked is that it can fix all the shunts at the same time. (I've seen them for sale for $10-20 so they're not as expensive as the one I linked above.)
posted by mekily at 12:03 PM on November 16 [1 favorite]


"TL;DR So...what if two bulbs are broken, or three, or more? Wouldn't I have to replace pretty much every light in that half of the strand to get it working again?"

Yes, but chances are that it is only one bulb. I have the patience to assume that all the bulbs are good, except one bad and that I don't know which socket has the bad bulb. I start with one new good bulb and try it in socket 1 (that does not light up), then, assuming it doesn't fix it, taking the bulb I just took out from socket 1 and trying it in socket 2, and so on until the strand works. If I get to the end and it doesn't work, then I toss the strand.

That approach fixes it 9 out of 10 times.
posted by bruinfan at 12:05 PM on November 16 [2 favorites]


As a side recommendation; I found that xmas lights last longer if they are not stored in a hot attic. I don't know if yours are stored there, but it's a bit of worthwhile info for anyone who's in a similar situation.
posted by mightshould at 4:00 PM on November 16


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