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Today I Learned How to Keep Christmas Tree Lights Working Forever

I have been decorating Christmas trees with incandescent mini-lights almost every year for many years. (LED lights are different.) Over that time, I’ve bought, maintained, and thrown away dozens of strands of lights. I’m cheap, so I always try to repair a strand when some lights go out, and I generally keep strands working for years. Eventually though, each strand gets to a point where I can’t get it working in a reasonable time, and I throw it away and buy a new one.

That is, until this year, when I learned how to keep Christmas tree lights going virtually forever!

Get a LightKeeper Pro

A while ago, I discovered a great tool to keep tree lights working when a light bulb or two goes out–the LightKeeper Pro (LKP)! It’s a super-useful tool–I think that everyone who lights a Christmas tree every year should have one. It has several functions, but the one I use the most is the quick fix–you plug your lights into the gun-shaped tool, pull the trigger a few times, and the section of your strand that was dark magically lights up!

It’s worth mentioning that most Christmas tree strands are composed of several sections of lights that are connected together to make a longer string of lights. For example, a 150-light string is actually made up of three 50-light sections connected end-to-end. (There are strings of lights that are composed of 35-light sections, but I don’t have any of those. These suggestions still apply.) When a bulb in one of the sections blows out, it will only affect its own section of lights. That’s why most of a long string of lights will remain working when one section goes dark. When I say “strand”, I mean one of these 50-(or 35-)light sections of a longer string of lights.

The LightKeeper Pro Isn’t Enough

Using the LKP quick-fix alone doesn’t keep your lights going forever though. I had some tree lights that had a bulb or two burn out every year or two and I’d use the LKP to get them working again. But then the entire strand of light bulbs blew out–every single bulb was blackened on the inside!

This year, as usual, the LKP fixed some of my lights before I put them up. After I fixed them and put them up, we finished decorating the tree. The very next day, a strand went out and the LKP didn’t help–all the bulbs were blown. Another strand completely burned out the next day! While I’d seen this happen before once or twice, this was the first time it happened to me after the tree was completely decorated. We decided to live with the burned-out strands for the duration of the season–removing the lights and ornaments, fixing the lights, then putting up the lights and ornaments again would have been too much work.

As I chewed on this frustration, I decided to figure out what caused this, and it didn’t take long to find out.

Replace All Burned Out Bulbs

The short answer is that every season, before you put up your lights, replace all the burned out bulbs. It turns out that as long as you start each season with all of your mini light bulbs working, the LKP quick fix will keep you going for the season.

You usually get a few replacement bulbs with each new strand. When you run through those, you can buy mini light bulbs in bulk online or at many hardware stores. (The number of bulbs in a strand determines the voltage of the bulbs you need to buy–2.5V for 50-bulb, 3.5V for 35-bulb strands–make sure to get the right ones.)

How This Works

If you just want to keep your lights working, you can stop reading. If you’re curious why these suggestions work, here are the details.

How Does The LightKeeper Pro Work?

It’s not magic, of course. I learned that each bulb in a strand has a little shunt built into it. The shunt’s job is to keep the rest of the bulbs in the strand lit even when its bulb burns out. Usually the shunt just works–when a bulb burns out, the shunt kicks in and the rest of the bulbs continue to work. Fairly frequently though, a bulb’s shunt doesn’t work right away, and the entire strand goes dark. That’s where the LKP comes in–plugging the strand into the tool and pulling the trigger generates a jolt of electricity that causes the reluctant shunts to start working, and the strand lights up!

Why Replace All The Dead Bulbs?

If you just keep clicking the LKP to get your strands working every year, more and more bulbs in each strand will be burnt out. Not very noticeable, but each strand is getting closer and closer to catastrophe. Here’s what’s happening.

When a strand is new and every bulb is lit, there’s a certain amount of electric current running through the strand. When one bulb burns out and its shunt kicks in, the same amount of current is going through the strand, but it’s lighting one fewer bulb. This causes each of the remaining bulbs to burn a little brighter. When another bulb burns out, the remaining bulbs burn a little more brightly. When a few more bulbs (5? or 6? maybe more?) have blown out, the remaining bulbs are running as hot as they can. The next bulb to die sets off a cascade of blown bulbs until every one is burned out.

A strand of lights can withstand a few dead bulbs, so just start the season off with no dead bulbs and your season will be merry!

The LightKeeper Pro Is Even Better!

There are a few more ways that your strands can go dark and the LKP can help you figure out the problem:

  • Every string of lights has a little fuse in the plug which can blow–the LKP has a fuse tester.
  • Sometimes, the wires at the base of a bulb can break. The LKP has a voltage detector that can tell you where the bad bulb is.
  • The LKP has a bulb tester, too.