Christmas Lights Troubleshooting Checklist

by | Oct 19, 2016

Where did I store those Christmas Lights?

I wonder what shape they’re in…. time to inspect and troubleshoot!

It’s only the middle of September but now is the time to start planning for Fall, Halloween and Christmas lighting.

Dust off your Christmas storage boxes and begin your assessment now.

Almost all of our lights are back in stock. We have a few types of LED Christmas light strings that have not arrived but they should be here within a couple of weeks.

Your Troubleshooting Checklist

Find those lights and start untangling them.  Here is your maintenance checklist:

  1. Do a quick visual check of your lights checking for frayed insulation and wiring – discard any light strings showing visible wear
  2. Inspect for damage done by critters over the summer – discard if the sets have been chewed
  3. Visually check for partially unseated and missing bulbs – this can happen when you stored them away
  4. Replace missing bulbs
  5. After a thorough visual examination, plug your strings of lights in – one at a time – to test.

Be sure to record the contents of your lighting inventory as you go through the stack of lights.

Don’t plug in light strings that have visible wear and damage. If the non-functioning strings are relatively new and are identical to others in your lighting stash, pull a few bulbs to use as replacements for your other sets and discard the worn strings.

Repair tips for incandescent Christmas lights strings (and LED light strings with replaceable bulbs)

Check the fuses

Everything was great, then the lights I was stringing together went out?  What happened?

You might very well have blown a fuse by exceeding the maximum number of lights one can run in series for your style of lights. Check the specs then verify how many lights you’ve run in series.

If you see that you’ve connected too many light strings in the same series run, reduce the number on the same circuit and start checking end-plug fuses one at a time and replace blown fuses as you find them.

Fuses more than likely came with your light strings and you may even have that little package of replacement bulbs and fuses stuck to your cord end – lucky you!

Examine your end plug. While plugs aren’t standardized, most Christmas light male plugs have a tiny little door on one of the wider sides.

Use a stubby screwdriver, gingerly ease it back (try to keep it straight to keep it “on the tracks”) and use a skinny long-ish screwdriver to remove and check the fuses.

These videos talk about the process.

Extra help to locate those fuses!

Check for missing or unseated bulbs

Many times, this troubleshooting step is the answer to the question:

What happened? My lights were working and suddenly half the string went out.


What happened? My lights were fine but half the string went out when I was installing the light string.

As a first step, visually examine and press in each bulb on the part (circuit) of the light string that is out.

Do not remove and reinsert each bulb.

Aside from rubbing the skin off your fingertips, more often than not, this can make problems worse instead of better.

Find an empty socket or broken bulb?

Hopefully, you’ve stored your “extras” that came with your light string in a labeled envelope and your next step would be to install or replace the missing or broken bulb.

If you have questions about how mini lights do or don’t stay on when a bulb burns out go out, watch the quick video on this post.

This issue might be “electrical” or in other words, there could be a break in the copper in the string’s wiring.  Perhaps the set was tugged a little too hard at the end of the last season or damage happened during storage.

If your lights are the victim of a dreaded electrical issue, it’s time to retire the set and purchase a fresh one. If the light string is relatively new, and the bulbs don’t show evidence of being smoked or worn, consider cannibalizing the bulbs from this string to donate to identical lights strings.

Troubleshooting tips for LED light strings with non-replaceable bulbs

One or two of my LED mini lights have gone out. What gives?

If the light strings are past a 1-2 week burn in time, most failed bulbs on an LED light string are due to surges on electrical lines.  The best solution here to prevent this from happening since light strings designed to be weather and water resistant by elimating connection prongs and the gaps between bulb bases and sockets can’t be repaired if single lights go out.

Note:  During those initial weeks, be sure to contact the manufacuter to explain the situation, receive troubleshooting advice and possibly get a replacement. (If you purchase your lights from Christmas Light Source, give us a call, we’ll walk through troubleshooting. We warrant all our lights strings for 90 days of normal, seasonal use.)

My entire LED light string suddenly went out! What do I do?

Sounds like an issue with a blown fuse.

Even though LED lights can be run with many more light strings in series than traditional light strings, double check to make sure you aren’t running too many strings in series and start checking fuses as described above.

These few steps solve 90% of the Christmas light string problems that folks encounter and allow you to plan and install this year’s display with fewer slowdowns during the process.

Be patient. And whatever you do, don’t pull those bulbs out one by one and reinsert them.

Just say no.

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  1. Norman H Theil

    Thanks good info. none of my lights work yet i can plug in another string & at the end of the string that dose not lite & they lite ?? THANKS

    • Shellie Gardner

      That sounds like an issue with the wiring harnesses of your light strings. It might be time to retire your non-functioning strings.

      If we had an easy fix for that, we’d love to share it. Sorry, we couldn’t be of more assistance.

  2. Chuck Stoeger

    Long story… need answer. I recently re-worked a gazing ball that has a 10 light set of Christmas-style mini bulbs inside the globe to shine at night. The 110 power source (adapter) is rated 3V – 700mA. There were a number of burned out bulbs & I used the white minis I have on hand. As I was checking the bulbs & replacing the burned out ones, I noticed that the further away from the plug (I had it plugged in) the dimmer the last 4 or 5 bulbs were getting. I need a way to resolve the problem & I tried to find the magical math answer on line somewhere. No luck. So what I need to know is the size for the mini bulb that will fix the problem. I graciously appreciate any help you offer. Thanks

    • Shellie Gardner


      The first and best thing to do is to check the tag that is near the male plugs on your sets to see if it lists the voltage rating of the bulbs themselves. That’s the information you need to purchase the correct replacements. Voltages for replacement bulbs come in various voltages such as 2.5 volt, 3.5 volt, etc. If you have the box the lights came in or know where you purchased them online, that information might be provided and help you choose the right replacement bulbs.

      Keep in mind that traditional mini lights last 2000-3000 hours and if they are in an enclosed space where some heat can build up – especially in the summer – this can shorten their lifespan. You might find it easier at this point to start over with a new string.

      (I wish I had a magical formula but I’m sorry, we don’t.)

      Best of luck to you with your gazing ball. I have one as well in my front yard with a string of lights inside and they are pretty, aren’t they?


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