I have a light to install that has the normal 3 wires, black, white, ground.
The ceiling has 4, black, white, yellow , and ground.

If I hook up the 3, black to black, white to white, grounds together, then the switch does not work, on and off by CB only, where does the yellow hook up to?

What are the wires in the switch?

Chuck

How was the old light hooked up?
Are you sure it is yellow? That is extremely weird. Could it be a very faded red?

Are these wires all in one Romex cable?