Question for the electrical / electronics gurus. What could cause a CB to remain stuck closed – i.e. when I pull it out it does not open the associated circuit? I already checked for the easy “there’s no circuit actually attached to it” answer :)
Corrosion/arcing leading to welded contacts?
Achim I reckon it shouldn’t be too hard to dismantle and clean oder?
Peter I checked for mis-wiring – nothing goes poof when I pull it.
Circuit breakers have a limited life span. I would replace, they are not expensive. I bet that a large percentage of GA circuit breakers would never trigger even if the avionics were to go up in flames.
In EASA land the Cessna landing / taxi light switches have to be replaced every x years which is nonsense but the circuit breakers can remain there for 50 years without triggering once or being tested. I plead guilty to having a bunch of 1979 circuit breakers that never triggered once 
Indeed, breakers can “wear out”, generally they become oxidised and the contact starts to fail.
That said, I’ve never seen one fail closed and this should be replaced ASAP as it poses a serious potential fire hazard.
Thank you all. Hopefully it is going to be easy work without needing to take the whole panel off.
What kind of acft is it ?
Most often they’re pretty easy to swap out although it may entail lying on your back and some mildly painful contortions
Mooney Ovation. It’s one of those the bottom row thankfully (the CB not the plane…)
It’s actually easier to access the ones on the top since you can easily remove the glareshield on the Mooney.
At any rate, should’nt be a problem.
ps: if you’re on FAA reg then you would be advised to get A&P supervision if Euro you better keep the hangar door locked
