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Spent 4 hours tracking a ghost voltage on a Cessna 172 last week
I was chasing an intermittent avionics bus fault on a 172. Multimeter showed 12 volts at the master relay when it was supposed to be dead. Took me 3 hours of pulling panels and checking grounds before I realized a tiny piece of metal shavings from a recent repair was bridging two pins on the back of the alternator control unit. Anyone else run into phantom shorts that drove you up a wall?
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finleym4312d ago
Man, metal shavings and random debris are the worst kind of gremlins, I swear. @hayes.joel you're dead on about foil being a common culprit, I've pulled a scrap of a gum wrapper out of a relay panel before that was causing all sorts of chaos. It's always the tiny stuff that makes you feel like you're losing your mind.
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hayes.joel12d ago
I once found a similar phantom short on a 172 that turned out to be a tiny piece of foil from a soda can stuck under the circuit breaker panel. Took me like 4 hours of testing and re-testing before I just started pulling breakers one by one and found it. I mean, the metal shavings from a repair is a good catch but I bet nobody checked for random debris like that. Idk, maybe it's just me but those little bits of trash are way more common than people think on older planes. Ground loops from a loose screw in the panel could also cause it, I've seen that too.
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