Our LED Electric Fence Light is designed for fence chargers that are 2-Joule or less . The Electric Fence Light let's you know that your electric fence is working good. As long as the light is flashing with every pulse of the fence charger it means all is OK. If the light is not flashing, it means that something else is drawing on the fence. Adjust the Spark Gap as wide as you can with it still being able to spark. This sensitizes the Spark Gap with your whole fence and if anything touches the fence it will get the full shock and the light will not flash at that moment. Remember the Spark Gap only draws current until something else touches the fence and it will not spark until whatever touched the fence is gone. Attn: The Z-Bulb Plus model is designed to replace the LED model and the bulb does not blow check this new design out with a guarantee.