How to fix a dead half-string of LED Christmas lights

Don't go be slicing them

 

As I am lazy, I keep our outdoor Christmas lights up all year. December 1 each year, I plug them in, and set the timer for dusk to 8 hours later.

This year, however, a bunch of the bulbs did not light up, right in the middle of them all -- as my wife quickly informed me. Inspecting it closer, I found it was half a string, precisely. Sixty-bulb LED Christmas lights are built from two half strings of 30 bulbs each.

There was no way I was going to replace the entire string, so I went online to see what kind of solution might present itself. The first several search results made me gag: people actually suggested cutting out the offending half-string and patching in another one. Actually.

I kept searching, and further down the list was a fellow who described in detail how strings of LED lights work, technically. See "LED Christmas Lights and How to Fix Them" by Terry Ritter.

One sentence jumped out at me: the string needs at least 75 volts to light up. That made my brain jump back to my Electricity 8 shop class:

What causes voltage to drop? 

Resistance.

What causes resistance?

Corrosion (among other reasons).

I got out some sandpaper and sanded the two dark brown prongs of the plug to a shiny clean brass color. Plugging the lights back into the outlet...

...

...the lazy lights sprang back on.

Merry Christmas!

 

 

Comments

[Jim Thoreson]

I have three sets of lights that are programmable using a remote control. Last year they worked, but his year, on two of the strings, only every 4th light works on the whole string. I have checked all the bulbs - AOK. The third string still works normally. I can't find any brand name on them, and can't remember where I bought them. Any suggestions on how to fix them.

[John R]

Interesting idea but -
the prongs were bright and shiny. and polishing didn't change their appearance
It is the first third of the string that is out, ie the third that is closest to the male plug.
If the problems is voltage drop there must be another factor at work.

Regards

John R

[Tom Ortega]

I have a string of LED Christmas lights with a problem , about 1/2 of the lights are on but very dim the other second half is on normal . The next string which is plugged in after the problem string works normal . Each string has a control to change the color & sequence which works normally

[Sandra Frat]

The first half of the string doesn’t work and the bulbs in this half are blackened from the base. Any thoughts?

[Ross_charles]

This type of light often has 2 circuits and if a bulb goes out, that half of the string will quit. You have to try each bulb on the dark half to find the bad bulb and fix the socket conductors or the bulb.

[Lynne H Baker]

We bought 5 sets of Noma C6, 70 light strands last year. When we put them up again this year, three of the sets had only half of the strands working. I didn’t keep the receipt, so after checking some sights, I did this, and IT WORKED! I first attached another set of lights in sequence and they lit up, so I knew the wiring was good. I then pulled out and checked each bulb in the unlit section, testing them in sockets that worked to make sure the bulbs were good. I had bought a couple of extra bags of C6 lightbulbs (5 per bag) when this issue was first discovered. I came to realize there were two sizes to the green bases of the lights when pulled out. A few were slightly wider than the others. The smaller ones would fit in all the bulb sockets, but the wider ones only fit in certain ones. After much fussing and frustration, I came to realize that the wider ones had to be placed in the first and last light socket of the strand, and also socket # 35 and # 36. If a smaller width one was placed in any of those four, the strand would go out. And Voila, all sets work again. If you have a longer strand, I presume this would still apply. The first and last, and the two exactly in the middle will need the bulbs with the wider plug in base.

[Russell]

I purchased 6 strands of programmable lights last year. They all worked last year. This year, every third light works on two strands. I can find my receipts for everything else, but these lights. I bought them at Lowes, but they aren't selling these this year. Any ideas on fixing would be appreciated.

[Christopher]

Put up outside led lights yesterday last year they all worked now only half seem to be working at intermittent spaces
cable looks ok tried contacting manufacturers but no response lights about 4 years old.

[Chris]

I have a problem I need help figuring out. Bought lights last year and they worked fine. Put them up this year and they were lit for 2 nights. I have a 3 80 count strands and a few shorter ones. Well one of the longer strands, the middle part is very dim.. The first third and last third are fine and the strand after.. just the middle section on the one strand. Has anyone seen this before and what should I look for?

[Cee J Trombley]

Thank you, Lynne H Baker!!! I thought there was something weird going on with the first and last sockets as was adding white bulbs to a multicolored string and if I put in the last socket the string would go out. Never in my wildest dream did I ever think it had something to do with getting the lights to work after I mixed up some bulbs! After hours of pulling them out and testing bulbs one by one and trying them on another string that worked before and then didn't, I decided to do a little research and Hallelujah! I didn't have to replace any in the middle. There was a sequence to the bulb colors and when I pulled a handful of the right color out for the beginning and end of the string I could see that there was a larger base on a couple to go into the socket. Nothing short of a miracle when it lit, lol. Well, hoping for a real miracle soon so we can all get thru covid. In the meanwhile, thank you Lynne! Merry Christmas all. :)

[Zale]

What about battery-operated lights? Brand new lights work for a few hours, then go out (or are very very dim), then start to get brighter, then work normally... then they go out again. Brand new lights, brand new batteries. Wiped battery terminals and batteries, replaced... no difference. Help?

[Helen]

I have noma SL08 - 3 strings.
They change from white to colour to other colours etc. However I cannot synchronize the strings even when they are on the same circuit. So one string is flashing, another is white and the 3rd is colours. I hate it.
They are remote operated and i use one remote only but cannot have them synchronize and all be the same colour.
Any ideas?

[Silvia]

My issue is the first bulb only works. I changed the next few after and still nothing works. They are brand new lights. I had tested them and they worked fine, but once I put them up and hung them, now it is not working.

[Manufacturer]

Thanks for sharing your experience. I managed to save two strings using your method.

[George Lehman]

I stumbled upon this thread and felt compelled to post this. I bought twelve 6 foot strands of LED Twinkling Icicle type indoor/outdoor lights. I tested each before installation and found to two of the twelve were only half lit. From the center of the strand to the end were completely dead. I returned them for exchange and the business gave me two new strands and told me to discard the "defective" strands. As the per-strand cost exceeded $20, I decided to attempt to determine the problem. After replacing fuses and checking that all the light were seated, I plug them in and found the problem had not been resolved. For some reason, I left them plugged in while on my work bench and walked away. About an hour later, I noticed that the lights that were previously dead were now dimly lit (very dim, though). After another hour, they were brighter. After four hours, all the lights were working and equally bright across the strand. I then tried the second "defective" strand. At first, the second half appeared fully dead. As with the first strand, after about four hours they were fully lit. I'm gobsmacked. WTF? In my 50 years of working with electrical items, I have never had one appear to "heal itself." Does anyone have an idea as to what's going on here?

[JLinn]

Did the same thing happen the next time the lights were plugged in like the next day?
johnl.
Below: The email address I entered is correct. Recd message that it was bad.

[Linda Ebersole]

Lynn H Baker’s comment helped me fix 3 strings last night that either had dim or unlit sections! There is something to the bases. Please be sure to check those as you replace bulbs!!!

[Bev]

I have a string of 150 c6 led lights worked fine when I plugged it in then half of the string went out ... suggestions