well first off, thanks Nico! I do know what a multimeter is. I am not talking about a multimeter. That would be something i would be talking about if he was looking for a required voltage or maybe continuity. I am not talking aout him looking for voltage. I once had a short in my headlight assembly for my truck. I took my truck to the dealer and they plugged my light housing adapter into a machine. The machine checked my wires for frays, or shorts within the wire itself (under the shielding) and at the connectors. It couldn't tell me where the fault was, all it could tell me was that there was a short somewhere. I just bought a new wiring harness and it worked fine.
Ok, now I know what machine your talking about - its called a time domain reflectometer... and you probably don't want to go buy one cause they aint cheap!
And I'm pretty sure you have open and short confused...
'Short' is a term used to describe a condition where two or more conductors are (normally) inadvertently connected together, such as when a wire is rubbing up against your frame, the insulation wears through and the wire becomes electrically connected to the frame. This is normally described as 'shorted to ground'
'Open' is used where a conductor has broken, or developed high resistance, such as when a wire is stretched and the conductor breaks, however the insulation may or may not. An open circuit can be described as not having continuity.
But yes, a TDR will check for open, short and impedance issues within a conductor, and tell you how far from the instrument they are.
You can do almost the same job that a TDR can do with a multimeter, it just takes a lot longer :)