I have a broken switch in my bathroom that needs to be replaced. It is the switch on the left which turns the bathroom light on/off. The switch on the right toggles a fan/light combo on or off in the same room. I would like to know if I can replace the dead switch on the left with a dimmer? If so, I need help wiring the new switch. As you can see in the image, the dead switch on the left and the switch on the right are connected to each other with a red wire. So there are two red wires connected to the upper screw on each switch. If at all possible, how would I replace the switch on the left with a Maestro LED+ Single-Pole or Multi-Location Dimmer Switch? The dimmer has one blue screw, one black screw, and one golden screw. There is also a green wire coming from the metal plate of the new switch but I don't see any ground wires connected to the old switch. Where would I connect the 2 red wires from the left switch on the dimmer? And where does the yellow wire connect to on the dimmer?
The red wire is certainly the supply (always-hot), and the yellow wire is certainly the switched-hot.
The red wire is a continuous wire that is hooked like a "U" over the screw. Don't cut it -- simply do the same thing on the new switch. This may take some fidgeting. Unscrew the screws all the way to the soft stop - do not force them farther than that, or you could damage the new switch.
You do not need to connect the ground wire. This is a metal box, and the dimmer will pick up safety ground via its mounting screws.