It takes a lot of work to locate either an open or shorted wire.  A connector will not normally disconnect by itself, but it can come apart if it was not properly connected..  You can sometimes locate the  problem by visually inspecting the physical wires.  An ohm meter will help a lot to locate an open wire (infinite ohms reading). A shorted wire will very likely blow out one fuse after another, giving you a point to start looking for the wiring problem.  An intermittent short is harder to find.  You need to attach the ohm meter to either end of the circuit and wiggle the wire along its length to "see" the ohms fluctuate when the wire shorts. 

   If the shorted or broken wire is suspected inside a "bundle" of wires, take your time and unwrap the bundle as close to where the ohms are fluctuating the most.