How to Test a Wiring Harness

Written by david lipscomb Google
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How to Test a Wiring Harness
Digital multimeters are ideal for testing continuity on a wiring harness. (multimeter image by dinostock from

Wire harnesses are used to connect two or more items, using a series of wires in one bundle. When one of these devices malfunctions, it's logical to test the wiring that connects to it. Using a multimeter is the best way to ensure that there is proper voltage and continuity along the individual wires in a harness.

Skill level:

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Things you need

  • Digital multimeter

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  1. 1

    Disconnect the end of the harness that feeds the device. For example, pull out the plug on the back of the vehicle's in-dash radio.

  2. 2

    Set the switch on the multimeter to "DC."

  3. 3

    Set the meter to the expected range of operation. In a mobile environment, that will be anywhere from 11 to 16 volts DC.

  4. 4

    Touch the black (negative) lead to bare metal on the vehicle.

  5. 5

    Touch the red (positive) lead to the wires in the harness that need to be tested.

  6. 6

    Turn the vehicle to the "ACC" position with the key. Observe the reading on the meter. It should read within the 11-16 volt range; most commonly, 12-13.3.

  1. 1

    Ensure the power to the harness feeding the device is disconnected.

  2. 2

    Disconnect both ends of the harness slated for testing.

  3. 3

    Turn the switch to the "resistance" setting on the multimeter. This setting is indicated by an image of an arrow pointing towards a positive ("+") symbol.

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