Originally Posted by moparx
Originally Posted by second 70
I saw the reply's from some people I respect on here and decided I needed to do more research. I'm always willing to listen and learn and I learned something new today.

Since 99.9% of my work is AC I needed to do some checking. Here's what I found was causing the difference of opinion.

Answer a DC test light is a tool with a normal open circuit that needs voltage to close to turn on light. So no it will not complete a circuit without voltage. Where an AC test light is just a closed circuit and will complete the circuit. ( yes I know it's a light bulb in a socket but that's all an ac test light is and i don't ever use them. I always use a meter).

The photo's show the ohm's and open circuit on the test tool.

I believe this source is still good info and would use a meter because almost ever car now has some draw (Clock,memory on radio & drivers ect.) that could turn the light on partially. Be sure and put the red lead in amp hole and set meter to DC amps. https://www.wikihow.com/Find-a-Parasitic-Battery-Drain




nothing to add, but i have the exact test light [black handle, serrated bulb case, wire color/size and clamp] you show, and have had that item for almost 55 years. biggrin
beer




Update I was WRONG!

I cleaned the ends on the tester and it's a closed circuit as well. The meter didn't have enough power to overcome the dirty connection but the 12 volt battery did. And yes it's old as heck. Lol