Neutral leak to earth
Mcb only control live.

yes. remove all the neutral, check one by one which one got low ohm to earth

check why low ohm first. could be something simple like the light socket busted.

ya if have the opportunity to lay new cable, do sekaligus live neutral earth.

the low ohmed neutral wire is removed, right?

check whole house, which socket or light does not work.

for socket, remove all plugged in devices, including extention socket

for light, remove if possible.


then use a multimeter to measure the ohm of the neutral to earth again.

ok great
i think its the fan because light bulbs dont have ground.

some crazy electrician install downlight using the earth wire as a hook. it is also possible the ground wire strand touched neutral.

Go get yourself a multimeter. You can try diy first
If fail only get the pro.
It's simple enough.

If don't have multimeter just connect back the neutral wire to the screw block

If found the rosak device then won't trip

You can get uni-t digital meter
Or sunwah analog meter.
The analog meter will be easier to use for your case.
The digital meter is more versatile