How to tell black wire from black wire?
I'm replacing a light switch in the bathroom. The existing switch has two black wires and I don't know which should go to the red wire and which to the black wire of the new dimmer switch.
The existing switch has one black wire that comes from the wall (along with a white wire for the receptacle) and is screwed at the top of the switch. The second black wire attached to the bottom is also attached to the bottom of the adjacent fan switch. The fan switch top black wire disappears behind the receptacle.
Can anyone help sort this out for me? Thanks!