Christmas String Lights Not Working

Strand of lights doesn't work? String lights in your dorm failing? Whether Halloween or Christmas lights, LED or incandescent, you can fix dark bulbs and get your string lights to turn on once more. Start with the simplest solutions and work up to the more challenging ways to fix a strand of lights.

If only half of your strand is out, check out our Half of Christmas String Lights Won’t Light Up troubleshooting page.

If you already know the problem, you may want to check out our guides for LED string light repair, incandescent light repair, and pre-lit Christmas trees. Remember that repairing Christmas lights saves tons of e-waste each year, and is even better than the energy savings gained by buying new lights with LEDs.

If the whole strand of lights is dark, first ensure that electricity is making it all the way to the strand. Tip: Plugging the strand directly into an outlet, not an extension cord or surge protector will minimize variables!

Bulb, bulb holder (or base), bulb in base, socket.

First check for missing bulbs. Many light strands will stay partially lit if bulbs burn out, but aren't able to stay on with even a single bulb removed. The contacts on the light complete the circuit.

• Install bulbs in any empty sockets:
• Plug a spare bulb into the socket—even a burned out bulb can help with troubleshooting, but a known good bulb is best. Your set probably came with spares, but the hardware store likely has bare replacement bulbs.
  • If you have a holder, but no bulb, thread the wires of a replacement light into the holders two holes, then fold the wires up around the holder. Install the new light.

Next check that the strand isn't damaged or cut.

• A cut in the wire will require a wire nut, or soldering and repair. Follow our wire soldering guide to cut out the damaged section, strip the casing, join the wires, then seal with shrink tubing (or if indoors and out of reach, you can try electrical tape.)

Next, check the circuit:

• Be sure the strand of lights is plugged in firmly.
• Be sure the prongs on the plug(s) are not corroded.
  • If the prongs look speckled, rough, or brown, they may be rusted, or corroded. Corrosion can prevent good flow of electricity. Use a contact cleaner or steel wool—or read the "Corroded Plug Prongs" section—to remove the rust and create firm contact between plug and outlet.
• Try using another outlet. If the strand works in the second outlet:
  • The first outlet may require a GFCI(or GFI) reset. Look for a red button in a nearby outlet, press it and try again.
  • The first outlet may be on a circuit with a tripped breaker. Check your breaker panel for any flipped switches and try again.

If the whole strand of lights is dark but the outlet has power, there may not be good contact between the lights and the outlet. Wear and weather can cause corrosion or rust on the plug's prongs can prevent good flow of electricity.

If the prongs look speckled, rough, or brown, they may be rusted, or corroded. Clean the corrosion off with:

• A pencil eraser.
• Contact cleaner, white vinegar, or isopropyl alcohol.
• Steel wool, a fine wire brush, or fine grit of sandpaper (at least 320 grit).

If the whole strand of lights is dark, the outlet has power, and the prongs are clean, your string may have a blown fuse.

1. Open the fuse door. The plug usually has a sliding door in the prong (not socket) end of the strand—slide the door towards the prongs with your finger or (carefully) with a spudger, or follow instructions printed on the plug.
2. Remove the fuses as you would a battery—some can be very stubborn—using your fingers or a spudger.
3. Look for a broken wire inside the fuse (holding them in front of a light can help)—or check continuity with a multimeter.
4. Replace any broken fuses. Your strand probably came with replacement fuses, but you can buy spares at the hardware store—the strand's plug usually lists the which kind of fuse to get

Strands with too many dead bulbs, or too many strands linked together can cause even new fuses to break. To prevent frequent fuse replacement, reduce the load by replacing dark bulbs and keeping to the manufacturer recommendations—usually no more than three connected sets.

Some light strands will stay partially lit when bulbs go out, others require every bulb to be in place and functioning. If all lights are dark, it's possible your lights are wired in series, or have a defect, and the bulb closest to power—or the first few bulbs—are dead, blocking power to the whole strand.

Remove each bulb to:

1. Be sure that the contact wires on the outside of the holder are intact, and in the correct orientation. If not, bend them back into place or replace the bulb.
2. Check to see that the filament (small wire) inside the bulb is intact and not burned out. If it is dark or discolored, it is probably burnt out, replace the bulb.

Tip: While removing bulbs check for corrosion or blockages in the sockets on the strand.

If replacing the first few bulbs with known-good bulbs doesn't work, check that there is a good connection between socket and bulb. Remove grime and other blockages with tweezers or a toothpick, and clean up corrosion(rust) with contact cleaner or isopropyl alcohol.

Tip: Tools like the LightKeeper Pro can help bridge broken circuits and further diagnose and fix problems. The video below demonstrates the use of the Quick Fix function.