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How To Find The Bad Bulb On Christmas Lights [Tips & Tricks]

Christmas is the time for fun, food, friends, and blinky decorations. Now, all those hours of effort on everything to just find out your blinking lights aren’t working? This would alone make some of our Christmas sours.

Now let’s be honest, in the string of tiny Christmas lights, it’s quite difficult to identify the faulty one. But today, I’ll make it less difficult for you.

How to find the bad bulb on Christmas lights?

The easy way is to use a Christmas light tester. Just hold the tester on each bulb of the string and watch it light up for the good one’s. Or use a non-contact voltage detector. In this case a dead wire would be the faulty one. For LED bulbs, turn on each bulb to detect the malfunctioning one.

Not enough information here, is it? I’ve got a whole article to help you out.

Now get into your Christmas spirits, you have bulbs to fix!

How To Find The Bad Bulb In The Christmas Lights? 3 Different Ways

Imagine you went out of your way to learn how to plug in Christmas lights without an outdoor outlet just for your lights to never turn on? A nightmare indeed. 

But Christmas lights come in this string and to figure the faulty one is an emotional war. And to get new ones at that eleventh hour might not be suitable .

Now, it’s time to do the next best thing. To become a handyman, fix it yourself and flaunt your skills to your Christmas guests. Who knows, this could be your time to shine as well.

Tools Required

To undo the dead bulb situation, you have to have some mandatory tools. Make sure to have them near you before you begin your job. Here’s what you need- 

  • Voltage detector
  • And/or Christmas light tester
  • A pair of safety glasses
  • Rubber gloves or plastic sandals
  • Functioning outlets
  • Replacement bulbs with perfect voltage settings

But First: Trouble-shooting

Let’s start by canceling out the obvious factor. This would help you to identify difficult ones later.

So, before looking for a burned-out bulb, you should look for-

  • A loose bulb
  • A burned wire
  • Probably damaged outlets or electrical plugs

To identify damaged outlets, you’ll have to have a multimeter, preferably the digital version. Also, you need to know how to use a digital multimeter to make any further conclusions.

Christmas lights or incandescent lights are wired in series circuits. This means if one is defective the rest won’t even start. So, it is important to identify the bad bulb instead of replacing the whole set to reduce waste.

With the right tools and steps, anyone can identify faulty lights and fix them. But first, it is important to identify the bad bulbs. Here are a few processes are given below:

Method 1: Christmas Light Tester

In this process, you need to own a Christmas light tester. Now, all you have to do is to bring the tester close to every light of the string and notice carefully.

A Christmas light tester’s indicator will light up if brought close to a functioning light. Which means, it will do the exact opposite in front of a faulty one.

Method 2: Non-Contact Voltage Detector

This one is the exact same as the Christmas light tester but for wires. Here, you would have to bring it close to the section of each bulb’s wiring.

The section where a lack of electricity flow is found, will be considered the dead end. Hence the defective bulb would be found there.

Methos 3: Good Ol’ Turn On And Off each

This method is applicable only for the LED bulbs. These bulbs are usually long-lasting, less heating and cheaper. But they are not lined up in a series circuit. 

So, you’ll be able to turn on each light from the string individually. And then detect the faulty bulb if you don’t have any voltage detector or Christmas light tester.

All you’d need is a replacement bulb to fix the LED bulbs. Even though the process is time-consuming, they are more reliable to invest in.

How To Fix Christmas Light Bulbs? Step-By-Step Guideline

If you have identified the fault in your lights, it’s time for you to fix them. Take necessary precautions because this requires exposure to open electrical wires. 

So, wear your safety glasses and your rubber gloves.

Now you’re ready to fix the light!

Step 1: Replacing the Bulb

After you have discovered the defective bulb, slowly take it out. Twist it from left to right until it loosens up and comes off. Take a look at the wires underneath. They aren’t supposed to touch each other and maintain a distance.

Then, take a new bulb and put it in the place of the previous one. The process is quite the same but this time twist it in the opposite direction.

Step 2: Fixing the Faulty Filament or shunt

Let’s start by connecting the light strand. And then unplugging any bulbs that are in or near the dark area. Then, by activating a piezo circuit, you have to insert the tool into the bulb’s socket and push the trigger. 

A high-energy pulse would go through the set. After that, any malfunctioning shunts should be reactivated after around 20 pulses.

Step 3: Replacing The Burned Fuse

If you see a fried fuse behind the plug, it’s time to replace it as well. Start by taking off the faulty one first.

Then take a new fuse with the same amperage and apply it in the place of the previous fuse. Try plugging in the lights to see if it works or not. 

If you have followed through the process correctly, check the voltage and amperage properly. But still, your lights aren’t working, get new lights.

Step 4: Upgrading The Lights

If you were using incandescent lights before, my gentle suggestion would be to switch to LED lights. Even though Led Christmas lights can get dim but they’re easy to use, cheap and long-lasting. To test them you don’t need many tools, just a lot more patience.

Here are a few of my favorite brands for LED lights below-

Product 1
Product 2

How To Protect Christmas Lights From Frying?

The only thing that should be fried at Christmas is your potatoes, not your lights. So, if you want to prevent a burned bulb situation, preserve it correctly for the next Christmas.

I know the best part of Christmas is the decoration and the worst part is taking off the decoration. But a little hard work will help you not to stress about next Christmas. Steps to be followed as prevention to light damage are-

  1. Remove the lights gently so that the strands don’t break.
  2. Inspect each strand before plugging in gently
  3. Store lights in bubble wrap so no bulb is broken
  4. Don’t overcrowd the light strands while you string them together
  5. It’s better to link strands together of same-coloured lights
  6. Never stretch your lights too much to plug them in. always plug them in the nearest strands.

So, here are the preventive measures to save your Christmas lights from destruction. Though it might occur to you if the common wire is hot or neutral, we would say don’t let the wire overheat. 

Even after all this, you find a defective wire, take it as heaven’s way of telling you to get new lights. So get the new lights.


Question: Why did half of your Christmas bulb stop working?

Answer: It’s probably because one of the bulbs is loose or broken. Start by wiggling all of them while they’re out, the faulty one will flicker.

Question: Why did my bulb turn black?

Answer: The filament of an incandescent light bulb begins to deteriorate over time, and particles gather on the interior of the glass.

Question: Can we recycle incandescent bulbs?

Answer: Yes we can. They don’t contain any hazardous material making them suitable enough to directly throw in the trash.


By now you must have learned every bit and bit about blinking lights. I hope you are now aware of how to find the bad bulb on Christmas lights.

But hey, if you haven’t been able to do it, it’s cool too. Just call a professional or get new ones. 

Until then, Merry Christmas!