I used to think the 'wiggle test' was a solid way to check connectors

I mean, for years I'd just give a wire harness a good shake and if nothing felt loose, I'd call it good. It was fast, right? But then last month, I was working on a Citation's autopilot system in Wichita and chasing an intermittent fault. I'd wiggled everything twice. Finally, my lead told me to break out the pin drag gauge on the D-sub connectors. I got readings all over the place on pins that felt fine by hand. Some were way out of spec, like 8-ounce drag on a pin that should be 3. That was the 'aha' moment. My hands just aren't sensitive enough to feel that. Now I feel like an idiot for trusting my feel over the actual tool for so long. Has anyone else had to unlearn a bad habit like that with a specific test?

3 comments

3 Comments

thomas_roberts9d ago

So what's the actual failure mode when the pin drag is that low? Does it just add noise, or can it cause a full signal drop?

william331mo ago

But is a few ounces of drag difference really gonna cause a failure in flight? Connectors are built to take some wear. Maybe the tool is overkill for most line maintenance.

caseyflores1mo ago

A few ounces? Are you kidding me? On a Citation autopilot, that's the difference between a solid signal and a flicker at the wrong time. You can't feel that wear, but the system sure can. It's not about the connector failing, it's about the data getting through clean. My old habit almost left a plane with a hidden problem. The gauge costs less than the hour you'll spend chasing a ghost.