I have a light switch for my garage on the inside wall of that room but not on the outside. I would like to add another switch to control the garage light so i can flip the light on from the laundry room when entering the garage. Instead of having to open the garage door and reach in and feel for the light to turn it on. I would pretty much be installing the new switch on the very opposite side of the existing switch. Can i just tap off that switch to run a new one?
So in the end i want:
A switch in the garage to control when you pull your call in and park.
Then also a double switch (1 laundry switch/1 garage switch) on the entry from the laundry room to the garage so i can flip the light on before i enter the garage.
You'll need to run a 14-3 or 12-3 depending on what size breaker feeds the circuit. Two of the insulated conductors will be used as travelers and the other as common. By code you have to use the white wire as the unswitched conductor.
So figure out which wire is constant hot and wire nut it to the white wire going to the switch location 2. Take the switch leg that feeds the light and terminate it to the common screw on the new 3-way switch at location 1 (that should be the black screw). At location 2 terminate the white wire to the common screw and the black/red wire to the other two screws, it doesn't matter which traveler goes where. Do the same with the travelers in switch location 1. You are also supposed to color or tape the white wire black if you want to meet code requirements, but electricity isn't racist so do what you want.