Hit 150 knots on the bench and my harness swap clicked

I used to think pinning out a harness was just a waste of time if the wiring diagram looked clean. Got a CRJ 200 that kept throwing a flap skew fault, spent 3 days swapping cards and chasing grounds. Turned out I had a pin pushed back halfway in the connector from a previous repair, wasn't even making contact. My lead told me to ohm it out from end to end, I laughed and said the schematic says it's fine. He grabbed me and walked me to the bench, we jumpered it up and the fault came right back with a resistance spike at 150 knots simulated. Now I pin out every harness before I even look at the box, saved me 8 hours this week on a 737 autobrake issue. Anyone else have a moment where a simple continuity test caught something huge?

2 comments

2 Comments

olivia_wilson19d ago

That bench test at speed is a great point, the vibration and air loads really expose those intermittent issues. A static continuity check on the ground won't catch a pin that flexes just enough to lose contact when things get moving. Simulating the actual flight conditions on the bench is the only way to be sure you're not chasing ghosts in the system.

thomas_roberts19d agoMost Upvoted

Last month I had a connector pin on a 737 that tested fine cold but failed after 10 minutes of vibration testing. We would have missed it completely without the bench speed setup. It turned out to be a hairline crack in the solder joint that only showed up under the heat and movement. Do you guys log the specific vibration frequencies that cause your failures?