I finally found a weird wire that was causing intermittent GPS dropouts

Spent all morning tracing a fault on a Cessna 172 that kept losing GPS signal mid-flight. Turns out a chafed shield wire was grounding out against a canopy frame, and I only caught it after my third continuity test with a Fluke 87V. Has anyone else dealt with phantom grounding issues that took forever to track down?

3 comments

3 Comments

tessa_clark741mo ago

wait hold on, I gotta push back on this a little. I know you're proud of finding that chafed wire, and yeah, it's a good catch for sure. but honestly, with modern avionics and all the shielding they've got, phantom grounding issues like this are pretty rare. most of the time when someone spends hours tracing a "weird wire" it's actually just a loose connector or a bad solder joint that got missed during the initial install. I've seen guys tear apart whole panels looking for a gremlin that turned out to be a corroded pin in a cannon plug. plus, if you're doing three continuity tests with a Fluke 87V, you might be overthinking it, man. sometimes you gotta trust your first instinct and check the simple stuff first. not saying you're wrong, just saying the easy fix often gets overlooked when you're chasing ghosts.

linda5001mo ago

Yeah, I read that loose connectors cause more phantom issues than bad wires.

hugo_schmidt20d ago

Oh man, @tessa_clark74, I read something in an avionics maintenance newsletter a while back that said loose connectors cause like 70 percent of intermittent electrical gremlins, more than actual broken wires. I remember thinking, yeah that tracks with what I've seen on older planes where the cannon plugs get all wiggly from vibration over time. It's wild how many guys will chase a phantom issue through the whole harness and it's just a connector not fully seated, especially on those Eurocopter models where the plugs are finicky.