I have a rather long string of twinkle Christmas lights. Half of the string works, the other half doesn't. What gives?

Sometimes one bad light can ruin the rest of the string, or a significant section of it. Something to do with currents…I think…not my area of expertise. I recall my mother explaining it to me when I was younger, though. I think the only solution is to replace the one that’s cut off the rest of the string, which means a bit of trial and error.

Individual lights can go out without affecting others if they’re arranged in parallel; if they’re arranged in series they all go out if one does. To have half out makes me think it was two series circuits connected in parallel? Does that even make sense?

@Mariah Kind of (haha). Is there anything that I could do to salvage the string?

I usually just look for the bulb that is causing the problem, and replace it.

I have that too. I wish I knew how to fix it. Last year, I rolled up the part that didn’t work, and used the rest of the string, and sometime during the week or two they were up, the rolled part started to work, so I’m guessing it was a loose bulb or something. I just left it alone, because the ball of lights look really nice.

As @ANef_is_Enuf says, if you can find the light causing the problem, usually just replacing that bulb will fix the problem. Usually the light causing the problem is the first light that’s out in that section, but sometimes it can be the opposite end or even the middle (depending on how the circuit is arranged).

If I have the patience I push on and check every bulb. Doing this while plugged in will usually result in finding a loose or broken bulb. I simply don“t have the patience to go to the next step and rotate a known good bulb through the lights that are out.
Long stings of lights do have segments in power and that is why a large segment is out. You also may have a wired broken going into one of the bases.

I just replaced most of mine this year with LED strings. The power consumption is significantly less (about 8–10times less) and you thus you can connect more end to end. They also do not see to be as fragile at the light end.

@blueiiznh “I simply don“t have the patience to go to the next step and rotate a known good bulb through the lights that are out.”

And then there’s always the possibility that two bulbs are out.

Is it safe to use it? The other half sure is pretty and I can hide the bad half.

@blueiiznh yes, that is the step after the single bulb rotation. I can’t think of a better way to spend my day than rotating mini bulbs

@Jude When at the bottom of the box of lights and all you have is a half functioning strand, I have been known to use it and hide the rest.

I can’t recommend the safety thing as without seeing it myself I would end up in fluther liabitity court

Check the fuse and the last bulb on the string.

If they’re wired in series, if the outage is linear so that all the working bulbs are consecutive, and it’s the same for all the unlit bulbs, then the bad bulb could be the one next to the last one that that works.

They should be safe to turn on at least for troubleshooting, unless turning them on trips a circuit breaker.

However, just to be safe, turn on the string, put tape on the bad socket to mark it, and then turn it off to replace the bulb.

If you have any spare bulbs, start at one end, pull out the bulb and replace it with the spare, if the string lights up, done. And the bulb you just pulled out is the bad bulb.

If the string doesn’t light up, the bulb you just pulled out is probably good. Pull out the next one and replace it with the one you just pulled out. If the string lights up, done. And the bulb you just pulled out is the bad bulb.
Repeat until you find the bad bulb.

The “bad” bulb could just be loose or oxidized, so as @blueiiznh alludes a twist or push can make that work.

I like the new LED strings a Lot because of their low power and low heat. But I miss the dimmability and still use a few incandescent strings for that reason.

I tried changing them out and it still didn’t work. Most likely, it was more than one bulb that was toast.

I ended up buying a new string of lights.