[Mgs] Electrical Problem diagnosis

[Robert J. Guinness]

As I am unpacking Christmas lights, I found a gift from last year that 
fixes broken miniature lights.  It has an audible continuity tester that 
works by passing the point @1/2 inch from the bulb or wire.  Could this 
be used to troubleshoot wiring on our cars?  See  
http://www.lightkeeperpro.com/support/how-to-use/audible-voltage-detector

Would it work on positive ground cars?

I am an electrical Luddite  --  so please do not laugh too hard.
-- 
Robert Guinness