Why do half my Christmas lights work?

So I went to Walmart because someone told me they had cheap lights. They weren’t the cheapest around, I found out, and they were cheaply made. I’m throwing a party for my other sister and for a little decoration, I decided to hang my X-mas lights around the room and on the ceiling. I plug my lights in and I have a bunch that just don’t turn on. I have other strings which have only half the string light up. Sometimes, if I drop it or jar it a bit, the entire thing lights up and will carry a current to the next set of lights. But, just a fickle as the first rough handling, a subsequent rough handling causes the lights to go off again. Sadly, I cannot reproduce that effect. What gives? Does anyone have a good idea of how to fix these lights? It’s really annoying, especially since I only got one season out of them.

On a somewhat related note, I’m finding it difficult to tape these lights to the ceiling (stucco house paint, type ceiling, but very cheaply done). Does anyone have any good ideas on how to keep the lights up there that doesn’t include too much damage to the ceiling. Masking tape works, somewhat.


They are apparently series-wired lights in two circuits. So, you’ll have three wires–one common, one for one string and one for the other. The idea is you can replace bulb #1 with a flasher4 bulb and make half the lights flash, or replace bulb #2 with the flasher and have the other half flash instead, or replace both #1 and #2 with flashers and have both sets flash. Unfortunately, if any bulb is loose or burned out, it will disconnect all the bulbs in that string. You can find the bad bulb easily enough if you have a non-contact voltage sensor.

First, plug in the lights. Then determine which string is out by unplugging first bulb #1 (the closest to the plug), then bulb #2 and see which one makes the lit string go out. Once you’ve found which one, leave it out and replace the other with a known good one. Now you can use your voltage sensor to find the bad bulb in the energized string. Run it along the length of the wire, starting at the first bulb in the string at the plug end, until the light goes out, indicating the circuit is dead after the bulb you just passed. Replace it or push it in tightly. If the string still doesn’t light, you might have another bad one. Continue with the voltage sensor to find the remaining bad bulbs, if necessary.

If both strings are out, repeat the procedure above with the other string.

As for hanging the lights, I’d recommend using small plastic drywall or stucco anchors with screw eye hooks. Once you’ve installed them, you can paint them to match the ceiling and leave them in full time. Probably not the ideal solution, aesthetically, but stucco is difficult to attach things to temporarily without pulling some loose.

BTW the above instructions apply to the common configuration of having every other bulb belonging to a given string. If the pattern is different, you’ll need to modify the testing procedure as necessary. Also, you can get non-contact voltage sensors in many places, including hardware and home improvement stores, electronics hobbyist shops, and electrical supply houses.

Wow, thanks for the answer. That seems like a lot of work. I think I’ll just buy new lights. Wait, what month is it? :frowning: (I’ll find lights from someone else)

Why do half my Christmas lights work?

Duh! Because it’s only halfway to Christmas (OK, It’s a little more than half).

Good thing you didn’t try them out in January. None of them would have worked.

It’s not as bad as it sounds from my description. And, after thinking it over, you can greatly simplify it by replacing this:

with this:

One string comes on if you wiggle it? As my electronic engineer friend would say, “that’s not electricity, that’s voodoo.” Throw that string away. Stuff like that spells FIRE! Christmas lights might just be the most cheaply made appliance in the world. Saving a few bucks is not worth burning down your house.