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I finally got why the old heads at Tulsa hangar swear by a $12 test light instead of chasing CAN bus codes by feel
Spent two hours at the Tulsa hangar watching a 30 year avionics vet trace a flaky pitot heat annunciator with nothing but a test light and a wiring print, and he found a chafed shield ground on the third connector where my $4k analyzer kept showing a clean bus, so now I want to know who else carries a cheap light before they break out the big box.
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cole_murphy14d ago
The "clean bus" part is what gets me, because a CAN bus can look perfectly fine while a ground shield is rubbing through on a bulkhead somewhere. The analyzer only knows what the bus reports, and a chafed shield won't always show up as a code, it shows up as a gremlin that comes and goes with vibration and temp. I'll push back a little though, a test light is great for chasing opens and grounds, but it won't tell you anything about signal quality or intermittents you can't catch in the moment. The old guys aren't smarter than the box, they just know the box can't see everything and a light never lies about a dead circuit.
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