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TIL a trick for testing a stubborn autopilot servo without pulling it
Had a Beechcraft King Air in the shop with a roll servo that kept failing the self test but checked fine on the bench. Instead of pulling the whole unit again, I used a spare 6-inch patch cable to jumper the feedback pins at the aircraft connector while monitoring the voltage. Saw a 0.3 volt drop that pointed to a bad splice in the harness run behind the panel, not the servo itself. Saved a couple hours of R&R time. Anyone else found a good way to isolate harness faults from LRU issues?
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wren_rodriguez2mo ago
Ever read about using a breakout box for this kind of thing? I heard some techs keep a spare connector wired to test points just for checking voltage drops in the circuit like you did. Your patch cable trick is basically the same idea, just simpler. It's smart because chasing a bad wire can eat up so much time if you just start pulling things apart. That small voltage drop you found is exactly the sort of clue you need. Makes way more sense than swapping a known-good unit over and over.
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gavinhunt2mo ago
Oh man, a breakout box sounds way too official for me. I'm all about the cheap and dirty patch cable method because it gets the job done. Honestly, if it works, it works.
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lilychen2mo agoTop Commenter
My old boss used to test wires by licking the stripped ends, which I do not recommend.
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