Tutorial: How to Make a Tester for Car Accessories

Sometimes you want to test a part before you put it on your car, especially aftermarket accessories such as fog lights. I will teach you how to create a simple source of power that you can use to test any 12V accessory.

You're going to need to find a small battery that makes 12V. I got lucky and mine came with an off-road light that I purchased. It was part of the package so you could press the button and see how bright the light is before buying it.

The directions also state that the battery is for testing purposes only so that's how I'm using it. You can make it yourself. The one I use has a button hooked up to it which is a good idea but you don't really need it. You should be able to find a pretty small battery that produces 12V.

This is how simple it is to build this:
1. Take your 12V battery and attach one wire to the positive side and another to the negative side. If you can't solder, it's okay, just make sure the wires have good contact and wrap it all in duct tape.

2. You can go ahead and install a button if you want. If you don't install an on/off button, just be careful to not let the wires touch but it's really no big deal.

2b. Installing a button is easy. You're going to connect your positive wire to the button and connect a wire from the button to the battery. When you press the button, it will allow current to flow. This lets you set up whatever you're testing before trying it. It IS handy.

Two and a half steps. Now you have a battery with two wires - a positive and a negative. Make sure you color coordinate that. Now you can apply those wires to the positive and negative terminals of whatever appliance you want to test.

See the light bulb in the first picture? I had problems holding it and taking a picture so I just set up my "wires" (in my case, I used some iron I had laying around) in a way where they are connected to the battery. This way, all I had to do was hit the button for power and take my picture. Mine is a little different. Yours will probably just have a positive and negative wire so simply expose some wire and you can touch those ends to your appliance.

You can see how I connected the bulb to the power source via two bent wires.

I used it to see if these two different LED bulbs I got shine the same. When I purchased them individually, I didn't realize they are slightly different. By taking a picture of both, I have a good idea of the difference - not much or zero. I'll be putting LED headlights in probably today. If I'm blinding people, I'll take it back off but I hope that's not the case.

Hope this helps somebody. I use that tester on everything. I'll find some lights, see if they work, and see if I can adapt them or something. It's pretty useful when you first start messing with electronics.

Have a good day, show your car some love, and come back.

- Rokas K.