Advice Please! Spaghetti mess behind old light fixture.

[jaliv]

I'm trying to replace an old light fixture and I've run into a mess. The fixture has an "always on" outlet that is likely contributing to the issue, but I can't wrap my head around how a single wire running from the switch turns into three pairs of cables at the outlet. Here are some photos, including behind the wall and a diagram of the wiring that I whipped up: http://imgur.com/a/DLBmB.

I was also going to install a combo switch where the outlet is, but I've discovered that I have what is called a "switchleg" and it looks like I will have to run standard service with a neutral wire to the switch box... something I'm tempted to do! Thanks for your feedback!

 

[Jadnashua]

One cable is your power in, that is wired to a second one that goes to feed something else down the daisy-chain, and the third one that has the white wire hooked into the black is the one going to your switch. It goes to one contact on the switch, and when that is on, comes back on the other. You'll notice that the neutral to the light and the other two cables are all tied together. The black from the cable on the right is only hot when the switch is on. You only need those two, and if you have any extras, you can just cap them. But, once you remove the leads from the always on receptacle in the old lamp, there shouldn't be any extra leads.

S0, on the new lamp, connect the ground to the others and the box, since it is metal, connect the lamps neutral (white wire into the other cables (in your drawing, the two on the left), and connect the black that went to the old light in the cable on the right to the black of the lamp.

 

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[jaliv]

Thanks for the feedback, I really appreciate it. Since I'll be losing the always on outlet and I can't use the combo switch for lack of a neutral wire, can I just add a neutral and a hot wire to the respective pigtail bundles and run them to a new GFCI that I will install nearby?

 

[hj]

It looks like you have enough of a mess without adding another cable to it.

 

[Jadnashua]

You can add another cable IF the box is big enough. Each cable, depending on the wire gauge, counts up, and there is a specific minimum box size required that needs to be calculated. But, assuming your box is big enough, or you can replace it with a bigger one that is, yes, you can just add another cable into that mix and run it to the GFCI.