Looking for ideas on how to follow a wire behind a wall. We just had about 80 foot of exterior wall replaced, that horrible T1-11 stuff replaced with Hardie board. Coincidentally, the GFCI breaker in my power panel, on the opposite side of that wall, will not reset, it trips instantly. I replaced the breaker, problem still exists. The power was off while they were working on the wall, so I have no idea what section of wall they were working on when the problem popped up. The hot and neutral are not shorted at all, infinite resistance according to my Fluke 87V. With only the neutral connected to the GFCI breaker, it still trips. So this leads me to believe the guys replacing the wall probably put a screw through the neutral somewhere behind the wall, and it's leaking enough current into the wall (S. FL everything is humid) to trip the GFCI. My question is, is there a tool I can connect to the neutral in the breaker panel, then go to the exterior wall and use it like sonar to follow that particular wire along the wall, potentially through conduit?