How To Use A Megger On Spark Plug Wires

Learn how to use a megger on spark plug wires to test the insulation capability of the wires and decide if they are faulty of not. Over time spark plug wires, much like the plugs themselves, can wear out and become faulty. A megger or Megohmmeter, is a device that you can use to test the insulation of electrical wiring to determine if it is properly insulating the current. Follow these steps for how to use a megger on spark plug wires.

To use a megger on spark plug wires, you will need:

  • Electrical gloves
  • Safety glasses
  • Work bench
  • Electrical tape
  • Megohmmeter
  1. Wear electrical gloves and safety glasses. Megohmmeters use electric current to test the insulation of a wire so it is best to take proper precaution to prevent injury.
  2. Open the hood of your vehicle. Disconnect one end of the plug wire from the spark plug and the other from the coil pack or ignition coil on your vehicle. Remove the spark plug wire and place it on an insulated work bench.
  3. Connect the positive cable of the megger to the one end of the spark plug wire. Connect the negative cable of the megger to the other end of the spark plug. Tape them in place using electrical tape.
  4. Turn the switch on the megger to the "On" position. Press the "Charge" button for approximately five seconds.
  5. View the meter on the megger. Ideally you want a value of 999 megohms. If the value is less than 1.5 megohms then the spark plug wire does not have the proper resistance and you need to replace the plug wires on your vehicle.
  6. Test each of the plug wires. Only remove one plug wire at a time so you do not get them mixed up. Most vehicles have different length spark plug wires. Replace all of the spark plug wires if you find a faulty one. This indicates that the plug wires are old and worn out.
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