Hi guys, have a problem.

Im my bathroom, we have a dimmer switch and a fan switch in the same box. Anyway, I turned the light on today, and the lights flickered and smoke appeared from the fan switch. I could smell that something burned.

I turned off the power and opened the box. On the fan switch, there are 2 screws on the side. The top screw looks OK, but the bottom one is black. It looks like it burned because I see some melted insulation that was on the wire. There are 2 black wire on the bottom screw and one white wire on the top screw.

I turned the power back on and everything seems normal. The lights work and the fan works.

Anyone know what happened? Is the fan switch busted or is there something more?
Thanks guys.

There are 2 black wire on the bottom screw and one white wire on the top screw.

Does that mean that there are two wires under the bottom screw. Or does it mean that two wires are connected to a pigtail (a third short piece of wire) and the pigtail connected to the switch?

but the bottom one is black

That indicates a short to something, probably the box if it is a metal box.

Having two wires under one screw would not cause the short to ground but it would make the screw extend out more than it should. That would make it more likely that the screw could come into contact with the side of the box.

Most likely what happened is that the switch is not securely screwed to the box and it moved and the bottom screw came into contact with the box.

Replace the switch. If you have two wires under the bottom screw, connect the two wires together with third, short piece of wire of the same size, with a wire nut. Then connect the third wire to the switch.

No, the two black wires are on the same screw. Odd, because its been fine for years and years. I suppose its possible it touched the box, though it doesn't seem anywhere near it. And yes, the box and switch are both metal. Hmmm, I was thinking. The washroom and my bedroom are on the same circuit (1 of the breakers shuts off power to my room and the bathroom). I have lots of electronics in my room, is it possible something is going on there? Though I suppose the breaker would pop if something was going on. Just wondering, would there be anything else I should look at besides a short? Just kind of worried at this point. Also, why does everything still work? The lights and fan still operate.

You turn on switch, switch moves. Moves close enough to box cause ark between screw and box. Screw and wire get hot, causes insulation to burn.
Replace switch and wire properly.