I just installed a new Leviton Switch for my bathroom exaust fan/light. After turning the power back on the fan is now on all the time and the switch only controls the light, all available wires are connected, not sure what's going on. I have 2 cables coming into the box where the switch is. One carries red, black, white and ground, the other is just black, white and ground. The switch i bought has only one black, red and white wire coming off of it. I assume connected one too many wires?
A photo of the wiring would help , but it sounds like you have 2 wires going to the fan and light and 1 hot and got them mixed up. Mark all 3 wires going to the switch 1,2,3 or a b c. Basically you need to swap the 1 wire that is all alone with one of the 2 on the other side. Now it will work or the light will be on all the time , if the light is on all the time the 1 wire on the 1 side of the switch needs to be swapped with the wire that has been on the other side all the time.