TIL my old way of tracing a ground fault was a total waste of time

For the longest time, I'd just start at the component and work my way back, checking every connection (which could take hours). Last Tuesday, a guy at the hangar showed me his Fluke 1587 megohmmeter and we found a fault on a King Air's autopilot circuit in under 15 minutes. The key was isolating the whole circuit first and testing the insulation resistance, not just continuity. It pinpointed a tiny spot of chafing in a wire bundle I would have missed for sure. Anyone have a different method for tracking down those sneaky intermittent grounds?

3 comments

3 Comments

stella_murray17h agoTop Commenter

Why do we always learn the hard way first?

miles94613h ago

My buddy Dave spent a whole weekend trying to trace a short in his garage wiring. He finally got a megohmmeter and found the bad spot in like ten minutes. I mean, he was so mad he didn't just do that first.

jones.anna19h ago

Yeah, that isolation step is everything, isn't it? You have to get the whole circuit dead and disconnected to let the megohmmeter do its job, otherwise you're just reading through other paths. It's the difference between finding the actual leak and just knowing the pipe is wet somewhere. I still keep a high-pot tester around for really stubborn intermittent ones, because sometimes you need to stress the insulation with a higher voltage to make a weak spot show itself. But you're right, it changes the whole game from a guessing hunt to a real test.