Three hours on a door switch that took five minutes to find

I spent half a day Tuesday chasing an intermittent fault on a MCE controller in an old office building downtown. Turned out to be a loose connection on the door limit switch that I had checked twice already. Has anyone else had a gremlin like that where you overthink it and miss something dead simple?

3 comments

3 Comments

andrew_baker96d ago

Checked the schematic after finding it? Bet the original installers ran the switch wires daisy-chained through three other devices. Gremlins like that usually trace back to someone saving two feet of wire ten years ago.

rowan_ross5d ago

A 2005 study on residential electrical failures found that over 60% of intermittent faults traced back to connections that were never torqued to spec in the first place. That loose switch leg you found? Probably just a hand-tightened wire nut that vibrated loose over a few years... not really "wear" in the normal sense. The original installer might've skipped the torque check on a Friday afternoon and that's the real root cause.

webb.hannah5d ago

Blame the installer all you want but loose connections happen from normal wear and tear over time.