I’m trying to replace a standard switch with a motion sensor switch. The box has a switch for the light and a switch for the fan. For some reason they are each connected by a black wire. There are also two black wires connected to he lower terminal and another one coming from the switch that goes into the wall. Am I able to cut the connecting wire? The replacement switch only has two black wires and the ground.
old light switch
new light switch
Switches need a connection to the always powered part of the circuit on one side of the switch and then the connection to the load (light or outlet or fan) of the other side. Often the live powered circuit enters the electrical box on one cable. If there are two switches in the box , like in your case, both of them need the always powered connection to that single incoming power feed cable. A very common connection method connects the power feed to the first switch and then jumpers over to the second switch to supply it power.
Given this it is most likely that you cannot just cut the black wire that bridges between the two switches.
Note that sometimes the incoming live feed may be wire nutted to two pigtail wires that in turn feed power to each of two switches. From the electrical standpoint these two methods are equivalent but look different that the switch to switch jumper to one not familiar with electrical wiring.
