How To Fix Christmas Lights

Determine What Kind of Lights You Have

Incandescent lights were the norm for Christmas lights for decades, but newer LED lights last longer and use less energy. If you’re using a Christmas light tester, it matters which kind you have because the testers are not always dual-use.

“Most [Christmas light] testers work well with incandescent lights since they operate on a simple filament-based system,” Kidwell says. If you have LED lights, buy a tester that is made for LEDs, or use a non-contact voltage tester or multimeter, which works on any type of light.

“Many testers can also handle LED lights, but some may not detect them properly due to their lower power consumption and different electrical characteristics,” Kidwell says. “It’s important to check the specifications of your tester.”

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Check the Circuit

If the entire Christmas light string doesn’t work, try these steps first.

• Verify you have power at the receptacle outlet using a non-contact voltage tester, or just plug in something else that you know works (like a lamp or another light string).
• Check that the breaker isn’t tripped, and reset it if needed.
• Check extension cords, if using, for physical damage (unplug first!).

Replace the Fuses

If the power is on but the entire string of lights doesn’t work, replace the fuses.

• Unplug the Christmas lights.
• Find the male end of the plug, and open the fuse compartment with a screwdriver.
• Pop out the fuses with the screwdriver.
• Test with a multimeter (set on continuity) or Christmas light tester, if desired, or just replace the fuses. (They’re inexpensive.)

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Check Bulbs and Wires

• Unplug the lights.
• Examine bulbs for loose connections. Sometimes tightening the bulbs may be enough to get the lights going again.
• Look for frayed or broken wires. If you find any, remove the bulbs to use as replacements and discard the string.

Test Lights With a Christmas Light Tester (Incandescent)

• Read the instructions that came with your tester.
• Make sure each individual bulb is snug in the socket. “Loose bulbs can give false readings,” Kidwell says.
• Plug in your light string.
• Run the tester along the unlighted length, or insert each bulb into the tester, depending on the style.
• Beeping or lights indicate the bulb works. You can also use the tester to remove and test individual bulbs and fuses.
• Replace bulbs that don’t work.

Pro tip: Incandescent Christmas light strings have an internal shunt within each socket to prevent a bad bulb from knocking out the entire string. Christmas light testers often have a mechanism to fix a faulty shunt. Just insert a single socket into the tool and pull the trigger several times.

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Test Lights With a Christmas Light Tester (LED)

• Read the instructions that came with your LED tester, then plug in your Christmas light string.
• Mark the section that’s out with clothespins or clips, or if it’s half of the entire string, mark the last good light.
• Unplug the string from the wall, and plug it into the LED tester.
• Start in the middle of the unlighted section. “If you’re troubleshooting a long string of lights, test in smaller sections to quickly identify problem areas,” Kidwell says.
• Grab one light and separate the wires going into and out of the socket, and insert one wire into the tester.
• Pull the trigger to send a small signal to the lights.
  • If the strand between the tester and the clothespin light up, you know the problem light isn’t in that section.
  • Mark this light as good and move on to the next section. Use the process of elimination to narrow in on the bad light.
• Replace the bad bulb with a new one, or use a replacement “pod” that comes with the tester.

Test Lights with a Non-Contact Voltage Tester

If you don’t have a Christmas light tester, test lights the old-fashioned way. This works for both incandescent and LED lights.

• Test your tester on a known live circuit to make sure it’s working.
• Plug in the Christmas lights, and separate the first dead light with your fingers so you have access to the wires going into and out of the socket.
• Use the tester to verify you have power going directly into the first dead light. If not, unplug the string, flip the plug the other way and plug it back in.
  • Most Christmas light plugs are not polarized and can be inserted either way. The lights work no matter how the plug is inserted, but for troubleshooting purposes, we want the power going into the light.
• Grab a light in the middle of the dead section and test each bulb’s incoming and outgoing wires. If you have power going in and out, you know the lights up to that point have power (and the problem is farther down).
• Work your way down the section, using the process of elimination to figure out which one is the problem bulb.

Test Lights Manually

If all else fails, use one good light string to test a bad one.

• Plug in your lights and find the bad section.
• Plug in a working light string. Use one socket from this string to test the nonworking bulbs on the other string.
• Place good and bad bulbs in separate bowls so you can easily replace and/or discard them.

Store Christmas Lights Properly

• Check them before and after use. Don’t put away bad lights. Likewise, check them before you put them up.
• Coil neatly. “Avoid tangling by coiling lights in loose loops; use a cardboard or spool to help,” Kidwell says.
• Label your lights. Keep outdoor and indoor lights separate so you don’t accidentally mix them up.
• Use storage containers: “Store in bins or boxes to protect from moisture and physical damage,” Kidwell says.

FAQ

How long do Christmas tree lights last?

Not very long. Incandescent holiday lights have short life expectancies, about 1,000 to 1,500 hours. That’s about one to three seasons, depending on usage. LEDs can last 25,000 hours or more in theory, but the abuse Christmas lights take means they probably won’t last that long.

How do you know if Christmas tree lights are unfixable?

A few reasons. “If the wires are frayed, exposed or melted, it can be unsafe to use, making repairs impractical,” Kidwell says. Likewise, if you have multiple bad bulbs, and replacing them doesn’t help, or the lights are old and inconsistent, it’s probably not worth your time to figure out.

How to fix Christmas lights on a pre-lit tree

Kidwell says the basic process for fixing Christmas tree lights is the same as fixing Christmas string lights. Check the power source and fuses, look for damage, check connections and test individual bulbs with a tester.

Who fixes Christmas tree lights?

Hopefully, after reading this, you do! But if that doesn’t work, or you have expensive lights and decorations that you’re not confident troubleshooting, call an electrician. Another idea is a sprinkler supply store. Strangely enough, sprinkler stores sell professional-grade Christmas lights and can help you troubleshoot or possibly even fix them for you.

About the Expert

Brandon Kidwell is an experienced electrician and virtual electrical expert at Frontdoor, a home service and maintenance app that connects qualified, on-staff experts to homeowners via enhanced video chats.