Discovered a trick for tracing intermittent faults in 737 ACARS panels

Been chasing a ghost on a 737NG for three days. The ACARS would drop out randomly during taxi but never in the hangar. Tried swapping the MCDU, the radio, even the antenna cable. Nothing worked. Finally got a tip from an old timer at SEA: put a USB thermal camera on the CMU can bus junction box. Found a cold solder joint that only opened up when the avionics bay hit a certain temp from engine heat. Reflowed it and it's been solid for a week. Has anyone else used thermal imaging for intermittent faults like this?

2 comments

2 Comments

robertb471d ago

Go grab one of those cheap USB thermal cameras from Amazon and point it at your home breaker panel sometime. I found a loose neutral wire in my garage that way, it was getting hot enough to melt the insulation slowly but never tripped anything. Same principle as your cold joint, just smaller scale and way less embarrassing if you guess wrong. A toaster, a space heater, even the cord on an old refrigerator, they all tell stories with heat that a multimeter misses until it's too late. It's like having X-ray vision for lazy electricity.

faith_carter1d ago

Slammed a thermal camera on a 787 APU starter gen last year chasing a no-start gremlin that only happened on hot days. Found a resistor in the voltage regulator that was barely hanging on, looked fine until the box hit 120 degrees. That cold joint thing is real, engines just bake those avionics bays and tiny flaws open up like clockwork. Nice work catching it before it stranded someone in Timbuktu.