How to Fix Christmas Lights Like a Pro

Annie Sisk
Written by Annie Sisk
Updated January 11, 2022
A family enjoying on winter holiday
Photo: luckybusiness / Adobe Stock

Stay holly jolly by repairing your Christmas lights in a few easy steps

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Nothing turns the family Santa into a Grinch faster than a string of holiday lights that won’t turn on. Whether it’s a few bulbs that refuse to light or an entire strand that stays dark, you’ve got two options. You could buy more strands of lights, which, if your time is limited, might be the best course of action. However, in many cases, you can identify the problem and fix it within a few minutes, using some widely available and relatively inexpensive tools—no electrician skills required. 

Difficulty: 1/5

Total Time: 15-30 minutes, depending on number of lights you need to test

Tools and Materials Needed: 

  • Voltage detector or holiday light tester* 

  • *Purchase a model that tests your specific type of lights

  • Safety goggles or glasses

  • Replacement bulbs with similar voltage rating

  • Working outlet

  • Empty cardboard paper towel roll

  • Multimeter (optional)

1. Visually Inspect the String

Before examining the bulbs, take a moment to perform a careful visual inspection of the strand. With the string of holiday lights unplugged from your outlet, check the string for more obvious problems, such as damaged or frayed wiring, or bulbs that are loose in their sockets. If possible, reinsert loose bulbs or, if they won’t give a good firm seal, replace them. If your strand has frayed or damaged wiring, replace the entire string with a new one. 

If the strand passes the inspection, verify that your outlet works. Simply plug in another string of lights or a small appliance that you’ve confirmed is in good working order. If you have a multimeter, you can also use that device to test the outlet.

2. Identify the Type of Lights 

Christmas lights are either incandescent or LED. The easiest way to identify which kind you’re working with is to plug in the strand for about 20 minutes, and then carefully touch a lit bulb to see if it’s hot. If so, you have a string of incandescent lights, which work by heating up a filament inside the glass bulb housing. 

If the lights stay cool to the touch after 20 minutes, then you have LED lights, which produce light by energizing protons that give off light when their energy level changes. In other words, LED lights don’t use heat to create light, so the bulbs don’t heat up. 

Of course, this method only works if at least one bulb on the string works. If the entire string is out, examine a bulb to see whether you can spot a filament. The presence of a filament generally indicates an incandescent bulb, though not always, as some LED manufacturers insert a “faux” filament to make LED bulbs look retro-chic. 

If you’re still stumped, read the string tag and look for any indication of the maximum number of bulbs you can run together in a series. Incandescent lights can handle up to five strings of 100 bulbs, or ten strings of 50 bulbs, while it’s possible to connect 20 or more LED light strings. 

3. Check the Fuse 

If the entire strand of lights is dark, a blown fuse might be to blame. Inside every prong power plug, you’ll typically find the fuses for your light string. To check the fuse, slide the compartment marked “Open” in the direction indicated by the arrow. Then, remove the fuses and hold them up to the light for inspection. The fuse is still viable if you can see an intact strand of wire between the two metal contacts.

You can find replacement fuses for your lights at most home improvement stores and major retail websites for around $10. Slide the small cover on the plug’s side to remove the old fuse and insert the replacement. 

4. Pinpoint the Broken Bulb 

If the string of lights is primarily working and only one or two bulbs are dark, it’s easy to pinpoint the bulbs that you should replace. (Hint: It’s the dark ones.) However, if the entire string is out, you’ll need to test each bulb individually to determine which ones you need to replace. 

Incandescent Lights

With incandescent lights, the electricity needs to complete the circuit through every single bulb. That’s why one bad bulb makes the whole string nonfunctional, although longer strings may contain two circuits, in which case only half the string stays dark. 

To find the bad bulb on incandescent strings: 

  • Place the light tester next to the first bulb in the string. 

  • Check the indicator on the tester. 

  • If the bulb works, the indicator will light up. If not, the indicator will stay dark.

If you’re using a non-contact voltage detector instead of a Christmas light tester, you’ll need to put the device near the section of wire between the bulbs. When you get to a dead section with no voltage, the dead bulb will be located immediately before that wire section without voltage. Replace the dead bulb with a new one. 

LED Lights 

You can check LED Christmas lights with removable bulbs using the same process as incandescent lights. Begin at one end of the string and use your voltage detector or LED Christmas light tester to check each section of wire or bulb, respectively.  

For a string of LED lights that’s completely dark, you can also use a more analog method to locate the bad bulb. Take a functional replacement bulb and, one by one, replace each bulb in your string with it. When the string lights up, you’ve pinpointed the bad bulb. You’ve also solved the problem, so you can move onto the next step of stringing up your holiday lights. 

5. Hang Your Lights

Hanging lights on a wooden pergola
Photo: Ursula Page / Adobe Stock

Now that your lights are all in dazzling and working order, it’s time to string them up around and outside the house. But if the thought of putting your lights up turns you into a Grinch, why not hire a pro to handle that part? A professional holiday light hanger costs an average of $415, depending on the size of your home, and their services will give you more time for other holly jolly activities with your family.

6. Store Your Lights Properly for Next Year 

After the holidays are over, take a few extra minutes to store your light strings properly to avoid repeating the bulb-checking process next year. Wrap the strand of lights carefully around an empty cardboard cylinder from a roll of paper towels. Store each strand in a container cushioned by newspaper or tissue paper for extra protection. These protective measures will help minimize the risk of damaged bulbs and frayed wires.

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