How to Fix Christmas Tree Lights

Nothing grinds the Jingle Bell Rock to a stop like a broken strand of Christmas lights. Replacing broken Christmas lights has become part of the holiday tradition for many, however. Like forests of evergreens sprouting in department stores across the country, faulty strands of flickering lights are an unmistakable sign of the start of the holidays.

There’s no need to ditch every darkened strand detangled from that familiar storage bin, though. With a few specialty tools and tricks, most broken Christmas lights can be repaired faster than a fresh batch of gingerbread men can emerge from the oven.

For starters, grab a pair of wire cutters, some electrical tape, clothespins and a batch of orange, plastic caps called wire nuts. A voltage detector and Christmas tree light repair device like the LightKeeper Pro or LED Keeper can make the job much easier.

Check the Lights for Damage

Before breaking out the staple gun or the double-sided 3M tape to mount your lights, save your future self some time by examining every string of lights on the ground. Look for cracks or splits in the insulation, exposed or frayed wires and damaged plugs. These are the most likely suspects for a bad string, and seriously damaged equipment should be disposed of, not plugged in.

Once your lights check out, plug them in for a test run.

Repairing Traditional Incandescent Christmas Lights

This is your chance to assess whether a malfunction is due to a faulty bulb or another issue. In the case of smaller light sets that are typically wired in a series configuration, electrical current flows sequentially through each bulb to complete the circuit and illuminate the entire set. If a strand fails to illuminate, your mission is to find the faulty bulb and replace it.

With traditional incandescent lights, the culprit may often not be broken at all. Be sure to make sure every bulb is tight before proceeding to a deeper dive.

Grab a multimeter tool to make finding broken bulbs exponentially easier. A tool like the LightKeeper Pro will help you discover bad or burned-out bulbs that can be easily replaced.

In larger sets of incandescent lights, two wires often direct current to sections of each strand. This explains how — sometimes — only part of a strand goes out. Shunts are a secondary device built into the base of each bulb that helps redirect current in the case of a faulty filament.

Replacing an Incandescent Christmas Tree Light Bulb

Some larger and older incandescent strands unscrew just like a light bulb in your home. For smaller, more intricate strands, a bulb removal tool makes changing faulty bulbs fast, but this process can also be done by hand. To replace a faulty incandescent bulb, place the base of the bulb in one hand and the bulb itself in your other hand. Gently pull the offending bulb out and replace it — ideally with a replacement bulb found in your original packaging — and carefully push the new bulb into place.

It's that simple.

Repair Shunts With a Piezo Circuit

These sound complicated but are incredibly easy to repair with a device like the LightKeeper Pro. To repair a shunt, plug in the light strand and remove the bulb in the dark section. Insert the LightKeeper Pro into the bulb’s socket and squeeze the trigger to create a high-energy pulse called a piezo circuit. After about two dozen pulses, faulty shunts in the strand will come back to life.

If this method fails, try using a voltage detector to determine whether or not the fuses are carrying enough current to power the lights.

Changing Christmas Tree Light Fuses

Christmas tree lights rely on tiny fuses to regulate voltage. Just like the fuses in your home or automobile, these fuses are easy to replace if you know where to look. On holiday lights, the fuse box is typically located behind a miniature compartment on the male end of the plug.

Use a voltage regulator to determine whether or not a fuse is blown and, if so, replace it. Replacement fuses can be found at stores like Target or Walmart or on Amazon for a low price and can typically be replaced in just a few seconds using your fingers. (Be sure to unplug the strand first!)

Repairing LED Christmas Lights

In recent years, LED Christmas lights have become a popular choice for homeowners seeking more energy-efficient and reliable lighting. Like their traditional counterparts, LED Christmas lights also contain a fuse usually located inside of a sliding door on the male end of the plug. Fixing a blown fuse is as easy as popping out the old one and inserting a new one — again, with the lights unplugged.

As with traditional bulbs, you’ll also want to check light strands for cracks, snips and defects in the wiring that might pose a safety issue and force you to dispose of the string. Typically, these manifest in flickering or darkening lights.

In addition to these universal challenges, LED bulbs and their typical array of color-changing options introduce some new challenges to holiday light repair.

Replacing an LED Christmas Tree Light Bulb

Replacing an LED bulb is a simple process, albeit one that is slightly more delicate than its more traditional cousins. To replace a blown LED bulb, firmly grip the base of the bulb and gently remove it from the socket by pulling away from the strand of lights.

LED bulbs often have two long leads connecting the light source to the current running through the wire. Be sure to place the longer lead on the side of the bulb base with the short, plastic key protruding from its rim. Then, gently push the new light into place.

Check for Broken Diodes and Blown Fuses

To put broken LED Christmas lights on the mend, grab a voltage detector or Christmas light repair gun.

LED lights do not have filaments that can burn out like incandescent bulbs, so you won't need to check for those. Instead, search darkened strands for an illuminated bulb adjacent to one without power. To do so, grab a voltage detector and plug the LED lights in. Place the voltage detector on the base of the bulb socket and check for power. If power is present, move to the next bulb.

If no power reads on the voltage detector, turn the male end of the plug upside down and insert it again. If you still don’t see power, you’ve found the culprit. Replace the bulb.

If you’ve acquired a repair gun like the LED Keeper, this process is slightly different: Plug the lights into a wall outlet; take the two clips provided with the repair kit and attach them to separate ends of the darkened section; unplug the lights from the wall and use the gun’s internal power supply to narrow down the broken bulb starting from the centermost bulb.

Repairing a Non-Replaceable LED Bulb

While most LED Christmas lights are composed of replaceable bulbs, some strands rely on bulbs that are permanently affixed. When these burn out, an entire strand can go down for the count. Not to worry, though. A pair of wire cutters and a wire nut will fix the problem in short order.

To repair a burned-out LED bulb that is not replaceable, you’ll want to identify the bulb, make sure the strand is unplugged and snip the two wires attached to the bulb casing.

After you’ve snipped the wire, strip away the outer layer of the wire’s casing enough to twist the inner copper filaments of both wires together and insert into a wire nut. Use electrical tape to encase the nut and the wires into a water-tight cocoon and proceed to rockin’ around the fully operational Christmas tree.