In alt.home.repair, on Fri, 20 Dec 2019 14:39:41 +0630, Oumati Asami
wrote:

The light in the laundry room stops working after worker had worked on
the ceiling in the next room.

There are two wires coming in to the light (or one in one out). Before I
flip the switch, both wires are not charged as tested by a tester. After
flipping the switch, both are charged. Yet, the light just won't light.

I removed the light and plug it in to a socket, it works.

Question:

1) did the test (both wires not charged and then charged after flipping
the switch) I do make sense?

2) how could the work in the other room affect the light next room? I do

I put a dimmer on the dining room light, got interrrupted in the middle
for a long time, then didn't know why the range hood didn't work. The
wire for the range hood came out of the box with the dining room light
switch. Of course the wall was right between the rooms.

You're using a real volt meter, not a neon light or something? The
lightbulb is not in the socket when you are testing the voltage to it?

see that there are three wires in the switch box, none of them neutral
or ground. They are all live wires. Two on one side of the switch, one
on the other side. The two are charged, the other is only charged after
the switch is flipped.

This is the switch for the light that does not work?

The "two are charged" when the switch is not flipped, but are both
charged when the switch is flipped?

Is there more than one switch controlling the light in hte laundry
room? Not very common but would account for there being 3 wires to the
switch.

Alternate question, are the two that are charged directly conneded
outside the switch, by a continuous piece of copper, or are they
connected inside the switch. (I'm assuming one is connected to the
other and the second one is hot only because it's connected. That's
probably true.)