12 Volt Circuit Probe

You Can build a 12volt Circuit probe that can be used to test for the presence of a 12volt potential voltage.

This is a very useful tool that has many uses.

You will need soldering iron, wire Stripper and a hand drill or drill press.

Tools Required

Hand Dril or Drill Press
Soldering Iron
Wire terminal crimpers
Flat Screw driver
Meduim metal file


Materials Required
(1) ½ x4” PVC threaded nipple
(2) ½ PVC threaded end caps
(1) 6-32x2” brass Machine screw
(2) 6-32 Brass nuts
(1) 6’ piece of 14awg Stranded black wire
(1) alligator clip
(1) ring terminal 18awg
(1) LED panel lamp with 6”+ pigtail
(1) 2” piece of shrink tubing

Make sure you have all of the part before you start and have a clear space to work.


Locate the (2) ½ PVC Pipe end cap and drill a hole in the end of each of them. One hole will need to be 1/8” and the other will be determined by the diameter of the Panel LED

Next drill a 1/8” hole in the side of the 4” PVC pipe nipple

Thread the Black 14 awg wire through the hole in the pipe and tie an over hand knot about 3” from the end.

 Install the Panel LED in to the pipe cap as shown.

5. Crimp or solder a ring terminal to the +12v side of the Panel LED (red wire).

 Strip the end of the black wire and Side a 2” piece of heat shrink tubing it. Solder other wire on the Panel LED to the black wire.

Slide the heat shrink tubing over the soldered connection. Using a heat gun or lighter warm the heat shrink tubing until it shrinks around the soldered connection.

 Slide the wire with the ring terminal through the pipe nipple so it sticking out the other end. And stuff the rest of wire into the pipe and screw on the end cap that holds the Panel LED.

 Now take the 2” brass machine screw and put it through the ring terminal. Next put on one of the nuts and spin it all the down to the ring terminal.

 Next Screw the Brass screw through the 1/8” hole in the other pipe cap.

 Next spin the other brass nut down and tighten against the pipe cap.

Stuff all of the wires in to the pipe and screw on the pipe cap with the brass screw.

Using a file or grinding wheel shape the end of the screw to a sharp point.

Strip the long end of the black wire and crimp or solder on the alligator clip.

Test your newly built 12v circuit probe on working 12v source