Power Probe ECT 2000 - Manual (Page 19)

19
Short Circuit Inside a Wire Harness
A common occurrence inside of wiring harnesses is that there are two wires running close and parallel to each other. One wire is the positive wire
that fl ows one way and the ground wire that fl ows back the opposite direction. When the signal source runs closely parallel to the signal return, as
in this case, they cancel each other and the signal strength is considerably reduced.
You can pull one wire at a time away from the other wires, creating some distance between them. As you hold the wire away from the other wires,
the signal canceling effect is removed in that area and the signal strength will increase in the wire. You can now get a reading off of the wire with
the SMART receiver by holding it parallel to the receiver’s pick-up area. Take note of the directional indicator of the SMART receiver. Check for
the other wire that indicates the opposite direction. You can now assume that both wires are in the same circuit. Trace both wires as a pair along the
harness until you fi nd the problem. (see illustration)
When supply and return signals run close and
parallel to each other, they can practically
cancel each other out to the point where there
will be no signal detection.
+ supply signal
– return signal
__________________
= 0 reception
Short circuit
inside wire
harness
English