How to Test a Faulty Ignition Coil Wire

Written by nathan fisher
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How to Test a Faulty Ignition Coil Wire
A simple continuity test can determine if a wire has short-circuited. (The Readout image by Cinneman from

Many electrical issues can be traced to loose or damaged wiring. Often however, the problem cannot be located through visual inspection, as the damage that is preventing current from travelling through the wire is located inside the wire's insulation. This can be especially problematic for fragile auto ignition wires covered by heavy insulation. For direct current applications, testing the integrity, or continuity, of a wire is a simple procedure that can be accomplished with a standard DC test light.

Skill level:

Things you need

  • DC test light

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  1. 1

    Remove the ignition coil wire from the ignition coil and distributor cap terminals.

  2. 2

    Attach one lead from the test light onto each metal terminal of the wire. If the bulb does not light up, you already know the wire is faulty.

  3. 3

    Wiggle the wire, gently, along its length and at both ends. If the light goes off, or blinks, it indicates the wire has a short and needs to be replaced.

Tips and warnings

  • Check the test light on the battery to be sure it is working properly and will provide you with a proper reading.
  • Do not wiggle the wire too vigorously, or you could damage it during the test.

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