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How to fix broken Christmas lights

Don't waste a light strand or risk using a broken one. You can fix it.

Alina Bradford/CNET

Got a strand of Christmas lights that just won't shine? More than likely, the problem is simple. 

Just one broken bulb or busted fuse can leave you with a dark strand and a sad looking holiday display. Here's how to figure out what the problem is and how to fix it. No mechanical or electrical knowledge needed.

Find a broken bulb

The first step is to look for any broken bulbs. If you can't find one, the next step is to plug the strand of lights in.

In some strands, when a bulb goes out, all of the bulbs after it won't light. These are series circuit lights that create a closed circuit. 

The current runs down the cord, through the bulb and out into the cord again to the next bulb. A broken bulb breaks the flow of electricity. In this case, the first bulb that is unlit is probably a bad bulb.

In lights that are attached in a parallel circuit, one bulb going out won't dim the rest of the strand because each bulb has its own source of current.

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How Christmas lights work.

Energy.gov

If you have lights with a parallel circuit (if they're LED, they have a parallel circuit for sure), you'll still need to replace the burnt out bulbs, but a huge section of the strand won't be affected. It will be easy to see which ones are bad when you plug them in. The bad ones just won't light up.

Grab a black permanent marker and mark each bulb that's bad so you know which ones need changing.

How to install a new bulb

Just like in a lamp, the bulb can be removed and replaced when it burns out. 

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Make sure to use gloves when fixing bulbs.

Alina Bradford/CNET

Here's how:

  1. Unplug the strand.
  2. Put on a pair of protective gloves and firmly grasp the bulb with your index finger and thumb. 
  3. Some bulbs screw in, so look to see if the base of the bulb is connected to the socket or if the bulb is inside the socket. If the bulb is inside, pull. If it's connected, twist the base. Pull the bulb straight up from the socket, though. Pulling at an angle can make the bulb break off in the socket. 
  4. If the bulb is already broken, use a pair of needle-nose pliers to pull the bulb from the socket.
  5. Your strand of lights came with a pack of replacement bulbs. Grab one and push it firmly into the socket. 
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Some bulbs are removed by pulling, others unscrew. This one unscrews and the colored light cover comes off. Underneath is a bulb that needs to be pulled out.

Alina Bradford/CNET

If the whole strand won't light

If the whole strand won't light, then chances are the fuse in the plug is toast. Take a look at the plastic box part of the plug, then pry open the little door with your nails or a flathead screwdriver. Some of these little doors slide open, so give that a try, too.

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Here's the fuse box on these lights. It slid open.

Alina Bradford/CNET

Inside, you'll see two tiny glass fuses. If they are black or the strand in the center of the fuse is broken, the fuse needs to be replaced. 

With a small flathead screwdriver, remove each of the fuses out by leveraging your screwdriver under the metal end of the fuse and popping it out. Replace them with the extra fuses that came with the lights. Just pop them into place and close the door on the plug.

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Strand of holiday lights come with extra parts.

Alina Bradford/CNET

If you don't have extra bulbs or fuses

Okay, not everyone saves that pack of extra parts that comes with the lights. I'm not judging! You can get replacement parts at home improvement stores. Your best bet is to take the strand with you to the store to ensure you're getting the right piece. 

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