Hot take: Tuesday was the worst shift I've had in 10 years of avionics

I spent 7 hours tracking down a ground fault on a King Air 200 that turned out to be a stray strand of wire from a previous repair buried under a bundle. The schematics showed nothing useful and the fault only appeared after the cabin warmed up past 80 degrees. Has anyone else dealt with intermittent faults that seem temperature sensitive like that?

2 comments

2 Comments

christopher95218d ago

Thermal expansion is almost always the culprit in those situations. The wire strand itself won't change resistance much with heat, but the problem is when that stray strand just barely touches a ground point after everything expands enough to close the gap. I've chased similar gremlins where the fault would disappear the second you opened up a panel and let cold air hit the bundle. Best trick I learned was to hit suspect areas with a heat gun while watching a sensitive meter - takes the guesswork out of waiting for the cabin to heat up naturally. Also worth checking the schematics against the actual build because those King Airs have had so many mods over the years the drawings are usually wrong.

webb.victor18d ago

...and that's the kind of thing that'll make you question EVERYTHING you know about wiring. So when the cabin finally got hot, did the resistance change in the wire strand itself, or was it more about thermal expansion making contact with something it shouldn't have?