I Attempted to Wire an Outlet in my Garage and power it off an existing switch. The switch is one of 2 that controls a single light. There are 4 wires coming into the switch Red+ Black+ white + ground. What do I need to do, to have Power always ON to my outlet? Thank You
Turn the light OFF. Check the COM (or Common) or C terminal of the switch you want to draw power from (typically black wire). If the light is OFF but you have power on the COM, then you wire that to the brass screws on the receptacle. You wire the white wires that are connected together in the box the switch came out of to the steel colored screws. There is another scenario where you have a 3-wire going to each of the switches, and the power comes from the fixture box but you would handle that the same way. Note that this solution may NOT meet your local code, and whether the reptacle works for your application depends on what you plug into it. You should hire a professional electrician if you don't understand how wire sizing and amperage loads work.
If you have two switches (with 3 screws each) and one light, then, yes, you might be able to power an outlet from one of the switch boxes, but only one specific one. Typically, a black wire, a white wire and a ground come from the breaker or fuse panel to the first switch. The black is usually 'hot', the white is 'return'. From the first switch to the second switch, you have black, red, white and ground. The black wire and the red wire take turns being 'hot', depending on the position of switch #1. White is still 'return', and ground is ground. At the second switch box, the second switch accepts both red and black as 'inputs', and outputs one 'black' wire. This black wire might be 'hot', or might be 'off', depending on whether both switches are in the same position or not. This black 'output' wire goes to the light, as does the white and ground. Since you have no way of determining which wire is 'hot' at switch 2, you can't hook up your receptacle as 'always on' there. You could tie it to the light though, so when the light is on, the socket is on. If you want the receptacle always on, regardless of the light, you need to connect it into switch box 1. Connect ground to ground, white to white, and use a marette or 'wire nut' to connect the black from the panel, the black to the receptacle, and the black to the 'common' screw.
I am supposing the switch is a '3-way', or SPDT. In which case the other switch would be similar. Power goes to one of the two, but not the other. You will need to re-wire both switches. The switch that gets the power needs to send (unswitched) power to the other switch. A wire coming from the light will need to be connected to neutral.
The wiring you describe is for a 3way switch which means another 3way switch is involved, probably in the house. You need to determine which wire is Hot all the time, this is the source of power for the branch circuit for this light. You can then split off from this wire an outlet which could be powered all the time. Using a test probe to the ground wire you can determine which of the wires is hot. You will need to toggle this switch as well as the one in the house to verify that one of the wires is ON all the time. I would suggest that you string another separate wire from the breaker box. Typically, you want a 20amp circuit minimum for an outlet. The lighting circuit may only be on a 15amp breaker, too small for your needs. NEC requires that a Garage Door opener be on a separate, appliance type, branch circuit.
