[Bill G]

I recently bought and returned an electronic voltmeter from Harbor Freight that was supposed to be able to register engine RPM. Supposedly, either from clipping the probe to the coil or using the coil wire pick-up. It did not work. It just registered random numbers on the display. I took it back and claimed it was defective. They graciously exchanged it. The second one did the same thing, so I took it back and did not ask for another one.

I don't know why it would not work, but perhaps because it needed 12-volt power instead of 6-volt.