How to fix Christmas light string wiring

Written by daniel england Google
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How to fix Christmas light string wiring
Christmas lights are renowned for breaking. (Polka Dot Images/Polka Dot/Getty Images)

Christmas light strings are notorious for not working when they are plugged in. This article will tell you how to diagnose and repair the fault. It must be pointed out that the equipment required for this task can be quite expensive while light strings are cheap, so don't undertake it unless you have access to a soldering iron or crimping tools! A basic knowledge of electrics is assumed.

Skill level:

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Things you need

  • Circuit Tester
  • Resistor (for LED light strings)
  • and
  • either
  • Soldering Iron
  • Solder
  • Heatshrink
  • or
  • Crimp tool
  • Crimps

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    Repairing Christmas lights

  1. 1

    Check the fuse. Replace if necessary. A simple circuit tester can be constructed with a battery, some wire and a bulb or buzzer. Do not plug in!

  2. 2

    Check plug wiring. Has a connection worked loose or fractured? Is it connected correctly? Do not plug in!

  3. 3

    Visually inspect the wire connecting the lights together and bulb holders. This is especially important if the fuse has blown as you want to determine why the fuse blew. Cut out any damaged sections and splice back together. As most strings have the same colour wire throughout, mark the wires before cutting to ensure correct reconnection. This is especially vital in the case of LED light strings. Don't forget to insulate soldered splices with heatshrink. Replace any damaged bulb holders. Once this is done is should be safe to plug lights in.

  4. 4

    Check bulbs . You may either replace each bulb in turn and checking if string lights up (but this won't work if you have 2 or more blown bulbs) or checking each bulb with a circuit tester (slower but more reliable). With LED strings direction of current is important so check both ways (on new LEDs the positive terminal is usually the longer leg, but these will have been trimmed). Replace faulty bulbs. I have found this is impractical with LED light strings as they are usually hard wired and insulated so each one has to be cut out, tested then replaced. Not a cost or time effective solution but sometimes replacements are not available or the string has sentimental value. When testing LED's make sure you use a resistor to limit the current.

Tips and warnings

  • Most new Christmas light strings are LED strings. Often you cannot access the bulbs to test and replace, but even if you can its a slow job. Throw it away!
  • Do not plug in until step 4.
  • There may be physical damage to your light string and therefore a risk of electrocution. Please do not attempt this unless you have a basic understanding of electric circuits.

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