How to Test Christmas Lights with a Multimeter

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The joy of a well-lit home can be turned into frustrations quickly when a burned-out bulb renders your entire string of lights dark. You might consider using a multimeter to assess the primary cause of blackout within your Christmas tree. Furthermore, it offers a convenient way of finding the dead bulb quickly, which will then require replacement in order to restore your holiday decoration into its fully lit glory.

When your Christmas tree fails to light up, you can solve it quickly with a DIY fixing. In this article, we shall be going through how to test Christmas lights with a multimeter. Furthermore, we shall provide you with a comprehensive guide on how you can identify as well as fix issues affecting your Christmas lights while using a digital multimeter.

The procedure of testing Christmas lights using a multimeter

Checking circuitry and fuses

  1. Ensure you have unplugged the string of lights, which is exhibiting lighting problems.
  2. Set up the multimeter to measure the resistance in your Christmas tree lights by following the manufacturer’s instructions. You will end up having two probes plugged in the multimeter.
  3. In one of the female socket, insert one of your multimeter probes.
  4. On the male plug, touch the remaining multimeter probe into one of the prongs.
  5. Once you have everything set up accordingly, observe the resistance reading on your multimeter. If it reads zero, touch the prong, which is on the other prong on your plug. If either of the prongs reads zero resistance, then your circuit is working end to end. However, if the result indicates a broken circuit, you should consider looking for damage visually and then retest it once the repair is done.
  6. Open your fuse access compartment that is located on the male electrical plug.
  7. Touch both of your multimeter probes to the opposite end of the fuse.
  8. Observe the resistance reading on your multimeter. If it is reading zero, then your fuse is in good condition. Otherwise, you should consider replacing it if the resistance is not zero. Once this is done, plug in your lights in order to determine whether there is any other necessary test required.
  9. If the problem persists, you should consider unplugging the lights and then begin assessing individual light bulbs to determine the problem.

Testing for faulty bulbs

  1. Commence the process at one end of the Christmas lights string that is darkened and then removes the first bulb carefully.
  2. On the bottom of the bulb, locate the two wires and then touch a probe on both cables. You should ensure that the probes don’t come into contact with each other or more than one cable. Your multimeter will then emit low voltage via the probes, which will test to whether a bulb has been burned out or not.
  3. Use the multimeter to assess for resistance presence. The resistance value of zero indicates that the bulb is functioning; however, you should get rid of a bulb if the resistance value is not zero.
  4. You should then insert the original working bulb or a new bulb into the position which is already tested.
  5. You should then move to the socket that follows and then repeat the same steps until your string is once again fully lit.

Assessing faulty wires

Before you plug in the strings to see whether the lights are working accordingly, it is advisable to take a couple of minutes to evaluate the item carefully. You should aim to identify faulty wires as well as damaged insulations. Wiring issues can lead to leakage of current if they are not tackled beforehand. This might even lead to severe injuries as well as electrocution.

Whenever you find an exposed or torn wire during this process, you should consider working on it immediately to avoid further complications and accidents from occurring. Here are critical steps to follow during this process;

First and foremost, you need to identify the missing insulation and wrap it using electrical tape where the wire is exposed. The electrical tape will help to insulate the exposed wire hence preventing any dangerous leakage from occurring.

You should mark around approximately an inch of insulation on every side whenever you locate a broken wire. It would be best if you then pulled it out using a pair of pliers.

To make a secure connection, ensure to twist the wires together and solder the joint in order for it to be more secure. For you to perform this, you should hold the soldering iron and the part of the wire than need to be soldered and apply the solder to seal the joint while it is still hot.

If this was the main problem within your Christmas lights, you can plug them into the AC supply safely, and they will work accordingly. However, if this was just one part of the problem, probably your lifts will not light up as expected. This means that you might be having issues with the plug.

Assessing faulty power plugs

If your Christmas lights aren’t working as expected, you should consider checking on your power plug. Sometimes faulty power plugs are the primary cause for currents absentia within a string of lights. Therefore, identifying this issue early will help you save your precious time. Here are critical steps you need to follow while assessing for faulty power plugs;

  • At the end of every power plug, place the probes of your multimeter.
  • Examine for resistance value displayed on the multimeter or the indicator light, depending on the multimeter you are using.
  • Your plug will only be fine if it indicates a closed circuit. However, if t does not, this means your plug is faulty. Therefore, you will have to replace it or maybe purchase a new set of Christmas lights if you prefer new ones.


Using multimeter in testing Christmas lights is a relatively straightforward process; however, you need to be cautious while dealing with open circuitry. Furthermore, it would be best if you considered insulating any broken wire as early as possible to prevent any accident from occurring.

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