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Christmas Lights Not Working? How to Fix a Dead or Half-Lit Strand

Updated November 1, 2026 · General information, not electrical or safety advice

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The short answer: Unplug the strand, then check in this order: the outlet (and its GFCI reset button), the fuse behind the small door on the plug, any missing or loose bulbs, and the sockets. A tester can find a bad bulb on small incandescent sets. If the wire is cracked, frayed or stiff, or fuses keep blowing, replace the strand.

Safety first. Use only lights and cords rated for outdoor use, plug them into a GFCI-protected outlet, keep ladders and light strands at least 10 feet from overhead power lines, and have a helper. Hire a licensed electrician for any wiring or new outlet. See our safety guide. This reminder is ours; the sourced details are on that page.

Work through it in this order

Unplug first. The retailer blog we read says to unplug before replacing bulbs. Do every check below with the strand unplugged unless a step says otherwise.
Check the outlet. iFixit says to plug the strand straight into a wall outlet, not an extension cord or surge protector, to remove variables. If the outlet is dead, look for a GFCI reset button or a tripped breaker.
Check the fuse. iFixit says the fuse door is on the plug at the prong end, and you slide it toward the prongs to open it. Look for a broken wire inside each fuse. The plug usually lists the right fuse type. The Department of Energy says the fuse is usually in the plug behind a small plastic door and can be replaced. The Christmas Light Emporium calls the fuse "the first suspect" if the whole strand is dark, and says that if a new fuse blows right away, the load is too high.
Look for missing, loose or cracked bulbs. iFixit says some strands stay partly lit when a bulb burns out, but others need every bulb in place. The Emporium says one bulb that is not fully seated can take out a whole section on many string types. Reseat any loose bulb.
Check the sockets. iFixit says to look at each socket's contact wires and to clean corrosion with tweezers, a toothpick, contact cleaner or isopropyl alcohol. The Emporium suggests a pencil eraser for corroded contacts.
Find the bad bulb in a half-dark strand. The Emporium says you can check bulbs one by one from the last lit bulb forward. Keep a known-good spare bulb to test sockets (iFixit).
Try a tester. Family Handyman describes a handheld tester that beeps along the wire at working bulbs, and says to replace the bulb just before the point where the beeping stops. It says that tester works only on miniature and icicle sets, not larger or LED lights.

Incandescent vs LED

Most of the steps above come from sources that describe small incandescent sets. iFixit says its page covers LED or incandescent lights but gives no separate LED steps. The Emporium says old incandescent sets reach a point where every fix reveals the next failure. For LED strands, follow the maker's instructions. See LED vs incandescent.

When to stop fixing and replace the strand

The Emporium says to replace a strand if several bulbs have failed, the wire is stiff, cracked or discolored, or fuses keep blowing with only one strand plugged in.
Family Handyman says not to use light strands with fraying or exposed wires, and to replace the set.
The Emporium says tape is only a short-term indoor fix for a small nick, and that exposed copper or melted insulation means the strand should be retired.
Do not splice a damaged outdoor strand yourself unless you know how to do it safely. That is our advice. iFixit describes splicing with a wire nut or solder and shrink tubing, and says electrical tape is only for indoor use out of reach.

Too many strands on one run?

Dimming at the end of a long chain means too many strands are in series (the Emporium). iFixit says usually no more than three connected sets, and the CPSC says never to string together more than three sets of incandescent lights. Check the box for your strand's limit and see the calculator.

Before you test the lights on the house, read the safety guide.

Strand beyond saving?

Pick outdoor-rated LED strings. Check the box for the wattage and for how many strands you can connect end to end.

Browse LED light strings Count what you need first

Common questions

Why is only half of my Christmas light strand working?

The Christmas Light Emporium says a single bulb that is not fully seated can take out a whole section on many strand types. Reseat the bulbs, check for missing or cracked bulbs, and test from the last lit bulb forward.

Where is the fuse on a Christmas light strand?

iFixit says it is behind a sliding door on the plug at the prong end. Slide the door toward the prongs, take the fuse out and look for a broken wire. The plug usually lists the right fuse type.

Does a Christmas light tester work on LED lights?

Family Handyman says the tester it describes works on miniature and icicle sets only, not larger or LED lights.

When should I throw out a strand?

The Emporium says to replace it if several bulbs have failed, the wire is stiff, cracked or discolored, or fuses keep blowing with one strand plugged in. Family Handyman says not to use strands with frayed or exposed wires.

Related guides

Sources