The Cessna 120-140 Association Forum

Hi New Member here.
I am a AP IA working on a friends C-140A and this AC has an electrical issue. As you add load to the DC buss by switching on the electrical loads starting with the master switch on the left then proceeding to the right there will eventually be a total loss of DC buss voltage. By switching off all the loads including the master and a brief wait, you can once again switch on the master and then additional loads until the trip re occurs. There seems to be a auto reset type of thermal breaker in the circuit that is tripping, cooling, then auto resetting. However I don't see such a breaker in the panel or when looking at the different electrical wiring diagrams, such as the early C-150's. Any feedback appreciated.
Brian in So CA

There aren't any auto reset current limiters, at least in the "as built" configuration. My recollection is they are not allowed, but a brief survey of AC43-13 comes up with "Automatic reset circuit breakers...are not recommended as circuit protection devices for aircraft." I take that to mean "good luck getting one approved".

If you wait but don't flip any switches, does it come back on line, even briefly? If not, than that pretty much lets out any "auto reset" device. My guess would be that flipping the switch is what is resetting it. Either that, or one of the loads takes a while to go into "overload".