Happy New Year to you all.
One of the more troublesome aspects of aviation electrical work is the fact our wires are usually NOT color-coded. That means you can have a bundle of twenty wires and before you can do any useful work you will need to figure out which one of the twenty at the equipment rack is the frayed one you've spotted behind the instrument panel.
How to do it? The good ol' fashioned way, which I described in an article some time ago, is to use a continuity tester. That is, a hunka wire long enough to run from here to there, a couple of flashlight batteries, and a flashlight bulb. You know you've found the correct lead when the bulb lights up. I even described a do-it- yourself tester based on an old-style Navy flashlight.
Alas, while 3 volts ain't all that much, you could be connecting those 'unimportant' three volts to a meter-circuit that blows it's top at two volts.
Whatcha REALLY want is a cable tracker.t
A cable tracker is a little oscillator that puts a warbling TONE on the wire under test, which you can then hear by waving a matching receiver at the other end of the wire.
Harbor Freight's gottem. Item #94181 about $20 US, probably less if you can find a Sale. (But Santa brought me this one :-)