Posts Tagged ‘test light’

My last post was on how to make a quick and easy test light. This is a little trick you can use to test your LEDs. Use this to verify which contact on your LED is the positive and the negative. If you think you have a defective LED you can use this to confirm if it’s the LED that’s not working or if your cars socket is the problem. Items needed to make this tester include a fresh 9 Volt Battery, a couple of lengths of wire and some electrical tape. This is easy to do, lets cover the steps.

Look at the picture below. Start out with your wire, tape and battery. Strip some sheathing off of both ends of the wire. Fold back the wire on one end. Note the positive and negative terminal of the battery and place the wire on top of each terminal. Fold the tape over and use it to hold the wire onto the terminals of the battery. And you’re done!  To use this new tool just touch the bare wires from picture #4 to the contacts of the LED, note which wire is positive and negative. If the LED  lights up you have the polarity correct. If the LED does not light up, reverse the wires and try again. If it still doesn’t light up than either the battery is dead or the LED is not working.

This little battery tester has helped me in may different ways. If you do not have a 9 volt battery, any battery will do. I have done this with power tool batteries too, just don’t use any batteries larger than 12 volts. You can use this for more than just testing LED lights. I first used this setup to test for speakers in cars when the radio harness was cut off. After I located all of the power wires I would use this to test the remaining wires to match up the pairs of speaker wires. And you can see the speaker move in or out too, which tells you what speaker wires are positive and negative.

I have had people ask me if you can get shocked by touching both wires at the same time, the answer is no. It is very rare that you would get shocked by 12 volts DC power; it is possible, but you would have to be trying really hard.

Thanks for reading. If you have another use for this type of tester of if you have another invention that you use on a regular basis please share. You can email me direct at: or leave a comment below.

James, the

Have you ever needed to troubleshoot a problem with your electrical system and there is not a test light around? Do you have a little MacGyver in you? If so than this quick little invention can be a lifesaver if you’re stuck in the woods or the local auto parts store is closed and you need to get some work done. If you are working on your car you most likely have the necessary items laying in front of you. If you’re like me you usually have random tools and supplies hiding under the seat from the last time you worked on your car. Regardless, the only things you need to build this test light are a couple short lengths of wire, a dome light bulb  and  some electrical tape. (If you are in a bind you can use any bulb from your car and any tape will work)

The steps are easy. 1) Locate all the necessary items. 2) Strip 2 Inches of the sheathing off of the wires. 3) Wrap the bare wires around each end of the bulb. 4) Tape the wires in place and strip about 1/2″ of sheathing from the other end of the wire.

This thing is pretty simple to use. If you need to find +12 volts just hold one of the wires to ground and touch the other wire to the circuit that needs testing. If the light turns on you have power.

If you need to find a ground you can hold one wire to +12 volts and touch the other wire to ground. If the light turns on you have power.

Hopefully you remember this when you need it most. Or you could just buy a test light and keep it in your car just in case.

Thanks for reading. Be sure to share this with your friends, you never know who might be in need of a test light.

James the