"Gunner" wrote: Indeed. I use them all the time, and they DONT work on DC
^^^^^^^^^^^^^^^^^^^
I have been using those for years. It's one of the handiest tools you can
put in
your shirt pocket. But, around the car, no. You need about 60 volts AC to
trigger it. However, you can buy a gizmo that clips onto the wiring in a
car, which injects pulses. You can then trace those pules around the car
using a hand-held receiver.

Incidentally, the little AC probe the OP is talking about can mislead you.
If the break is in the common side of the circuit, it will indicate you have
power. Say your pistol drill won't run, and the "chirper" says it should.
Don't immediately start pulling the drill apart.