How to Test Christmas Lights with a Multimeter (Guide)

One of the most common problems when using Christmas lights is when there is a break in the connection or particular connections to lights break down.

Below we go through the steps and give you a guide so you can make sure all your lights are working and troubleshoot any breaks in the connection including fuse replacement and bad bulb tests.

Troubleshooting Christmas lights are pretty simple. It is just a couple of steps which include:

  1. Check the wire for continuity
  2. Set up the multimeter
  3. Test string for continuity
  4. Test for bad bulbs
  5. Start at one end of the string
  6. Pull out the bulb and separate the wires

How to Test Christmas Lights

christmas lights

Everybody wants to have fully-working Christmas lights that will give their trees that extra oomph! Or light up rooms with a bright light.

Christmas lights range from about 25 feet to anything over 30 feet. When buying, I would encourage you to first test your Christmas lights by plugging them in so that you ensure everything is in good working order.

A multimeter, can be used to check Christmas lights, and also repair them by doing a simple continuity test. It is your best tool when troubleshooting Christmas lights.

red multimeter

Step-by-Step Guide for Testing Led Lights

The steps to do after buying tree led lights include the following:

Test the String for Continuity

When doing a continuity test, ensure that the holiday lights are laid out and all the parts are visible to make sure you aren’t missing anything.

testing christmas lights with multimeter

You can do a continuity test by:

Set-up the Multimeter

If your holiday string lights are one full length, you will need to then set up a multimeter. You can get a digital multimeter online or in any electrical store. I would advise you to choose a digital multimeter since it is better and easier to use rather than the analog one. First, connect the two probes of the multimeter. The red probe goes in the mAVΩ hole. The black one is connected to the COM hole on the multimeter. Although it will still read even if you connected it incorrectly, this is the correct way of doing it.

Test String for Continuity

You will then need to set the multimeter to continuity mode. This checks the connection between two points and determines if they are well connected. To set it to continuity mode, look for a diode symbol on the multimeter knob. Then touch the two probes together. This will produce a low tone. If your led Christmas lights are not working, continuity is the best way to check for that.

Christmas Light Fuse Replacement

When half of your Christmas lights are not working, it could be that you have a blown fuse in the lights. You can sometimes tell by sight if a fuse has blown since the metal filament inside will be broken. If this is the case, you will need to change the fuse. This is an easy yet important step towards ensuring that your broken Christmas lights are working. You will need to remove the old fuse carefully. Using a screwdriver or a pair of pliers, slide open the cover for the fuse and replace the old one with a new one. For most led Christmas lights, they usually come with an extra fuse that you can use. You can also buy the relevant fuse online or at a hardware store near you.

christmas light fuse

All this will guarantee no damage is caused to the tree lights and that they will work perfectly when supplied with power.

Test for Bad Bulbs

This is the next important step. Below, I will show you how can test for bad bulbs and change them. Broken Christmas lights will not light and thus be useless.

You can test for bad bulbs through these simples’ steps which are:

  • Start at one end of the string. You can roll out the strand bulb lights into one long length. Then, starting at the end of one string, roll out the bulbs one by one.
  • Pull out the bulb and separate the wires. Separate the wires and check if the wires are in good condition. Do this for every bulb carefully checking all of them. If they are in good working order, you can then return the bulbs to their position.

What if Two Bulbs are Burned Out?

christmas bulb light

If two or more bulbs are burned out, you will need to replace them with other new working bulbs. I would advise you to ensure that the burned bulbs are correctly replaced to ensure the lights remain in good working order.

First, ensure that the power is off and unplugged. Then, start with the one nearest to you working your way down. Wiggle the bulb a little and then remove it. Swap the burned-out bulb with a new bulb and work your way down the string of lights.

NOTE: A burned-out bulb will reduce the lifespan of the other bulbs since they would be supplied with more current.

After removing all the burned-out bulbs, plug in the lights and switch the power on and check to see if all the bulbs are lit. If there are unlit ones, you might consider repeating the above process until there are no more unlit bulbs.

Lights Won’t Stay On – Use a Splitter

After you repair the broken bulbs, plug in the Christmas tree lights and switch the power on.  If the burned-out bulbs were correctly replaced, the whole strand should light. If the light won’t stay on, you can use a splitter.

The lights won’t stay on because of the size of the string, and the amount of power passing through it. This can be solved by using a splitter. This connects two or more devices to the same power source. (1)

You can use this to connect two long strings to the same power source so that the whole string will be on and will light up.

How to Fix Flickering Christmas Lights

If the lights are flickering, this could mean that one or more of the bulbs is not correctly installed. You could try wiggling the bulbs a bit and check whether they will work. This is a good method to ensure that the Christmas tree lights are not flickering anymore.

Can you String Too Many Christmas Lights Together?

Yes, you can. Although this will depend on the type of bulb and the power supplied to the strands. I would recommend you connect a maximum of five strings. Though today, there are some lights that you can connect up to 50 lights.

How Many Lights Can Get Hooked on One Power Outlet?

xmas lights

The LED string lights can have up to 43 end-to-end Christmas lights connected using only one power outlet. This is the number that they can take at a time. (2)

Wrapping Up

People usually end up throwing away their newly bought Christmas lights instead of fixing them. Here we taught you to test Christmas lights with a multimeter so you can avoid any broken Christmas light blues.

Before you go, we’ve reviewed some of the best multimeters. You might want to check them below;

(1) power source –
(2) LED –

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.