How to Wire a Low-Voltage Idiot Light

by David Weedmark Google

    A low-voltage idiot light warns you when the voltage in a circuit drops to an unsatisfactory level. They can be used in a variety of circuits, so how you wire the light depends on what you are using it for. Before installing your own idiot light, you should be intimately familiar with the electrical system you will be working on. LED lights make ideal idiot lights, but because they use two prongs as leads, they can be difficult to wire and then mount. Using a shielded wire and then placing the LED in the threaded housing of a neon lamp indicator makes the LED much easier to work with.


    Step 1

    Consult the documentation for your equipment, including wiring diagrams to determine where you will install the idiot light.

    Step 2

    Determine what voltage level you want to activate the idiot light. Purchase a voltage monitor chip corresponding to this level.

    Step 3

    Select a shielded wire to accommodate the voltage of the voltage monitor. For example, to have the light warn you when the voltage drops below 11 volts using an 11-volt voltage monitor, you can use a 12-volt wire.

    Wiring a Secure LED Light

    Step 1

    Cut the end of a shield wire with wire cutters so the end is square. Strip the wire using wire strippers to expose 1/16-inch of the center wire. Strip it again to expose 1/16-inch of center insulation below the wire. Strip the outer jacket to expose 1/8-inch of the braided shield. Tin the center wire with solder using a soldering gun.

    Step 2

    Cut the long lead on an LED light to a length of 1/16-inch using wire cutters.

    Step 3

    Hold the base of the long lead on the LED light with a pair of needle nose pliers. Wrap the long lead around the wire's braided shielding so it coils around the shielding.

    Step 4

    Solder the cut lead to the center wire. Solder the coiled lead to the braided shielding.

    Step 5

    Cut the base from a neon lamp indicator, leaving only the threaded portion. Remove the lamp from the housing. Slide the LED light into the lamp housing. Secure it in place by filling the housing with epoxy. Wait for the epoxy to set.

    Step 6

    Secure the housing on the wire using electrical tape. Alternatively, you can use a heat shrink applied with a heat gun.

    Testing the Light

    Step 1

    Disconnect the battery from the system you are working on.

    Step 2

    Solder the wire to the voltage monitor according to the manufacturer's instructions. Wire the light and monitor to your system where required, connecting one end to a ground.

    Step 3

    Select a battery corresponding to the voltage level of the voltage monitor. For example, you can use a 12-volt battery to test an 11-volt idiot light.

    Step 4

    Connect the battery to your wired system and then activate the system. You can do this, for example, by turning on lights on a panel. The lights draw power from the battery, dropping the voltage to below 12 volts. The idiot light should turn on almost immediately.


    • Don't work on electrical systems you are not familiar with. This could result in injury or even death while working on the system or if the light fails to work properly after it is installed.

    Required Items

    • Voltage monitor
    • Shielded wire (braided shielding)
    • LED light
    • Neon lamp indicator
    • Battery
    • Wire cutters
    • Soldering gun and solder
    • Needle nose pliers
    • Epoxy
    • Electrical tape

    About the Author

    A published author and professional speaker, David Weedmark has advised businesses and governments on technology, media and marketing for more than 20 years. He has taught computer science at Algonquin College, has started three successful businesses, and has written hundreds of articles for newspapers and magazines throughout Canada and the United States.

    Photo Credits

    • Stockbyte/Stockbyte/Getty Images