Krafty Farm Assistant Farm

Spark Plug Fence Tester

The quick and easy, take anywhere way to test an electric fence.

Spark Plug Electric Fence Tester

What you need:

  • 1 spark plug, (can be an old spark plug as long as it works)
  • 500mm if insulated electric fence wire
  • 1 length of rubber hose (or soft plastic pipe) that fits over the tip and ceramic part of the spark plug (approx 100mm)
  • 1 plastic bungy gate handle
  • Insulation/duct tape

How to build:

  • Strip enough insulation from the electric fence wire to wrap around the top post of the spark plug and wrap the exposed end around the threaded post.
  • Replace the screw on tip on the spark plug until tight, (Hint: a small washer either side of the wire can be used to ensure better contact however ensure the washer is no larger than your hose.)
  • Slide the small piece of hose or soft pipe down the electric fence wire and over the spark plug until it covers the entire ceramic portion of the spark plug.
  • Apply enough insulation or duct tape to either end of the hose to hold it in place.
  • Strip the other end of the electric fence wire ensuring enough cable to join to the spring of the plastic gate handle.
  • Tightly wrap the electric fence wire onto the spring of the plastic gate handle. (Hint: soldering the electric fence wire to the spring may be an option if a soldering iron is available.)
  • Wrap the join with a small amount of insulation/duct tape around the join and allow to spring to retract back into handle.

Job complete

To test simply hold the spark plug by the hose or soft pipe and hook the plastic gate handle on the electric fence. Providing the tester is held by the insulated parts only no electric fence current will be felt by the user.

The smaller the gap in the spark plug the less voltage is required to make the spark and therefore the more likelihood of finding fences that are only just working however with some adjusting of the gap you can also get an idea of the voltage in the fence or make a tester which only works if the fence is at the desired voltage.

While not an exact science as a guide a 1kV spark will jump about 1mm, so if you are wanting a 5kV fence gap your spark plug fence tester to 5mm.



Krafty Farm Assistant has tried and tested this tip however it is provided with no guarantee or warranty and Krafty Farm Assistant takes no responsibility for the item or actions of those making it.