Signal drop in the hangar at 2AM had me chasing a ghost for an hour

I was doing a pre-flight check on a 737 at the FBO in Wichita and the transponder kept losing lock every time I moved the harness near the aft bulkhead. Turned out a grounding strap had worked loose behind the panel, not a bad box like I figured. Has anyone else had intermittent faults that only show up at night when the temp drops?

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haydenburns2d ago

Man, I gotta push back on this one. Grounding straps and loose hardware don't care what time it is, that's just physics being physics, and I'd bet money that fault was there in the daytime too and you just happened to bump the right panel at 2AM. What probably threw you off is you were tired and chasing it in the dark with a flashlight in your teeth, so your brain went straight to the worst case instead of the simple stuff. Nine times out of ten these intermittent gremlins are just a chafed wire or a loose connector that only acts up under vibration, not because the ramp got cold. Temp swing can mess with connectors and solder joints a little, sure, but I'd check your multimeter and your patience before you blame the weather.

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