Electrical mystery.....

Power Probe 3 is the one you want.

There are videos on powerprobe.com explaining all the functions better then I can.

https://www.amazon.com/Power-Probe-...ocphy=9005547&hvtargid=pla-376660908451&psc=1
Dam guys, I rewired my whole car about 8ish yrs. ago, and don't have any of that stuff !
I have a home made test light I made out of a tail light bulb/ no socket .
The first thing I thot of was the lead bulb contacts, grounds, rusty socket. He did say he switched bulbs and it worked !~!