I bought an ECT200 and Powerprobe 3 as part of my restoration kit, and they have paid for themselves many times over already.
Yes, the ECT200 struggles a little with wires in shielded spots, but it has a couple of tricks up its sleeve...
1/ The units sends a signal down the wire, and it emits an audible beep which changes when the short condition changes.
2/ The sensor unit LED points toward the short.
In one case on my Airstream, I was chasing a dead short in the 12v
feed to the horn and 12v
power sockets(cigar lighters).
I followed teh wire behind the drivers side panel, where it disappeared... in undoing the screws holding the panel on, the tone of the unit suddenly changed, indicating that the short had ceased...
Upon inspection, I found this main feed wire neatly split dead center by the trim screw!
So, by using the sound of the unit, and the direction of the short indicator, you can see where you have access to the wire, which direction or run the short is.
Then pull or manipulate wires and narrow down the areas, and see and hear what causes a change.