One thing to keep in mind about electronic short detectors, is that they search for magnetic fields caused by current flow. The thing that you have to watch out for is if there are any relays that are currently energized. Some of the tools will pick up an energized relay as a false signal due to the magnetic field with in the relay coil.
My preferred method for detecting shorts in fused circuit 10 amps or higher is to use a halogen head light bulb. To use a bulb, make a harness long enough so that you can sit the bulb off to the side (the bulb gets very hot). On one end of your harness use terminals to fit the bulb, on the other use spade terminals the same size as the fuse blades.
Then plug the bulb harness into where the fuse connects and turn on the key. If the bulb illuminates, you currently have a short. At this point you'll want to SLOWLY and gently start touching/moving the wiring harness. Start at one end while checking the bulb to see if it goes out when you get to a specific area. If it does then your close to the fault!
If the bulb doesn't illuminate when you turn the key on, you can still use it. Only in this case your watching for the bulb to illuminate when you get to the suspect area.
For fused circuits less then 10 amps I use a 194 bulb instead, as they only draw about an amp instead of the 6 to 7 amps that a halogen head light bulb draws. This is so that you don't overheat the smaller gauge wires in the lower amperage circuits.
