Where does this blue wire come from?

where is the other ends of the 2 yellow wire? need to find them and connect them to 0 and 2.

the bottom part of door bell one of them connect to black, the other connect to the live yellow

Noted on test lead as blue wire.

Colour mismatched cables will be rather tricky to test for continuity with power running. I worry that one of the gate post wires are actually 230V live.

If you have a long enough spare wire and a multimeter can try to check 1 by 1 wire (turn off the whole DB box) from the gate to the doorbell point inside (separate them out using a spare connector block) for continuity. It may have been mixed up or they are using half of yellow outdoor and half of black indoor. Or worse, hooked up the gate post wires into DB box. Macam macam can happen.

By right it is 5 wires at doorbell.
3 from MCB box to doorbell. 230V.
2 from gate to doorbell as unpowered (for low voltage) as dingdong button trigger.

I'd test the gate post wires to see if they light up a test pen.

many funny² things can and have happened in my experience.
see WRT DEVELOPER WIRING in https://forum.lowyat.net/index.php?showtopi...ost&p=100869300

Not all banglas know what they're doing.

Yup.

But depending on what house is he stay in.

Condo or landed.

If condo, I guess should be ok since the switch no exposes to rain.

Since it is already wiring, it would be headache to rewiring again.

2 option to solve the problem I can think of.

Option 1.
Take away the L wire from the DB and extend it to the doorbell. Now the 2 yellow wire can join to the low voltage transformer side of door bell and the switch. (safe)

Wire another L (240v) to the doorbell main side. This can use back your purchase door bell.



Option 2.
Get a wireless door bell with come the remote switch that run on battery. (Some new doorbell even don't need a battery for the remote switch)

Join the 2 yellow wire in the outdoor hub. Makesure the join doesn't expose to water. Now the internal yellow wire is L. Join the wire to the door bell.



Both are safe to use the switch.