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Coworker swears by the wiggle test on cannon plugs, I think it causes more problems than it catches
Had a intermittent fault on a pitot heat circuit in a King Air 200. Spent 2 hours with a Fluke 87 backprobing the cannon plug at the wing root and everything rang out fine on the ground. Coworker comes over, grabs the harness, wiggles it hard, and the reading jumps all over. He says thats the trick, always wiggle it. I say thats how you create the fault you are trying to find, flexing 20 year old pins. Now we argue about it every time something is intermittent. Which side are you on, wiggle or no wiggle?
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sageburns27d ago
The part about flexing 20 year old pins is the real issue here. Those cannon plugs have been sitting in one position for two decades, the wire bundles have taken a set, the pins are probably already got a little corrosion or fretting on them. When you grab that harness and yank it around you are moving stuff that was never meant to move like that, and yeah you might make the fault show up, but now you have also put stress on every other pin in that plug that was fine. I have seen guys wiggle a connector and turn one intermittent into three, and then you are chasing ghosts for a week. The Fluke on the ground tells you what the circuit looks like in the condition it lives in, which is bolted down and not getting yanked on. If you want to test for vibration, get the plane running or use a proper shake rig, don't just grab and twist. Wiggle test catches the fault your wiggle created, not the one the plane actually has.
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