How to Test Positive and Negative Wires When Wiring a Ceiling Light

Written by gary hancock
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Before installing a new ceiling light, you need to make sure that the power supply is off; otherwise, you risk a dangerous shock. The traditional method of checking is to use a standard Voltmeter or Multimeter to touch the exposed wires. For the novice, a safer method is to use a Non-Contact AC Voltage Detector, which can detect current through the wire's plastic insulation.

Skill level:

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Things you need

  • Non-Contact AC Voltage Detector
  • Flat head screwdriver

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    How to Test Positive and Negative Wires When Wiring a Ceiling Light

  1. 1

    Remove the light bulbs from your existing ceiling light fixture.

  2. 2

    Unscrew the light fixture from the electrical box in the ceiling.

  3. 3

    Pull the light fixture away from the ceiling to expose the wires coming from the electrical box.

  4. 4

    Make the battery is installed in your Non-Contact AC Voltage Detector and that the device is turned on.

  5. 5

    The light fixture should have three wires: a positive (hot) wire, which should be black but sometimes is red; a negative (neutral) wire, which should be white; and a green or bare copper wire, known as the ground wire, which should never carry an electrical current.

  6. 6

    Place the tip of your Non-Contact AC Voltage Detector anywhere on the positive (black) wire. If a current is present, a light will illuminate on your voltage detector. The negative (white) wire does not carry a current unless the power to your light fixture is turned on and a bulb is in it.

  7. 7

    If your voltage detector has not detected electrical current, you can safely disconnect your old fixture and wire a new one.

Tips and warnings

  • Working with electricity can be dangerous, even deadly, if the proper precautions are not taken. Before installing your new ceiling light or any electrical fixture or appliance, you should make sure that the power supply to the area where you're working is turned off.

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