automotive short circuit finder

What can i do to build this instrument that could help me a lot to identify short circuits in 12 v and 24 v systems.
Thanks.

Wouldn't a 'multimeter' work well enough? Basic continuity and voltage shouldn't be much of a challenge for a $6 (canadian) meter. Been a while, never used one myself, but there use to be a simple tester that looked kind of like a screwdriver. The bit was a sharp point, inside the handle was a light bulb, and a wire with an alligator (roach) clip on the end...

Use an ammeter that you just place near the wire and a 10 or 15 amp circuit breaker that resets its self. Every time the breaker comes on and trips, the needle will jump in the direction of the short.