Last year I hung a whole strand of lights, climbed down, plugged them in, and watched half the string stay dark. Then I had to take them down, find the bad bulb, and rehang everything in the cold. This year I do a ten minute check on the ground first, and I have not hung a dead strand since.

The ten minute test

Before anything goes on the house or tree:

1. Plug each strand in and let it run for five minutes. A strand that works cold can still fail once the bulbs warm up.
2. Look for dark sections, not just a fully dark strand. One bad bulb can kill a whole section in older strings.
3. Check the fuses. Most strands have small fuses inside the plug. If a strand is dead, pop the little door, pull the fuses, and look for a broken wire inside. Spare fuses usually come taped to the cord or in the box.
4. Inspect every bulb socket for cracks and every wire for chew marks or bare spots.

How to fix a dead section

With older incandescent strings, a dark section usually means one bulb is out or loose. Start at the dark end and work back, gently tightening each bulb and testing. With LED strands, the bad bulb is often hidden, so I test by swapping bulbs from a known good section until the dark one lights.

If a strand has frayed wires or cracked sockets, do not repair it. Throw it out. Lights are cheap and a shorted strand is not worth a roof fire.

Labeling saves next year’s you

After the test, I wrap each working strand around a piece of cardboard and tape a note on it: where it goes and how long it is. I learned this after untangling forty feet of unlabeled wire one December. It takes one minute per strand and it makes next year’s setup genuinely pleasant.

Also check the weather rating on the box before hanging outdoors. Indoor strands belong indoors. I found that out the wet way once.