Trying to install some track lighting so decided to do some investigating. There is a light switch in the room that controls nothing in the house. I've tested every outlet on the circuit and no change. Opened it up and see that there are 3 wires. One white, one black, one red. The black and red and screwed onto the right side terminals and the white is screwed into the top left. Testing the wires, both black and red are hot so it would appear that this switch is in the middle of the circuit. Examining the crawl space behind, I cannot see where the whiles lead. How can I determine what this switch was supposed to control? The majority of my house uses switched outlets and I would imagine someone just forgot to connect this one up. I would like to use this switch to control the new lighting so determining the outlet would facilitate this matter.

A switch with 3 contacts means a 3 way switch. So it could be wired to something you already know is controlled by another switch. Another possibility is that it only controls half a duplex outlet. The other half could be on all the time or even controlled by a different switch. You may need to do some more detective work.

If it's a old house -- might be a ceiling fixture that's been plastered over also

If its a old house -- might be a ceiling fixture thats been plastered over also

80s style home. No fixtures at all so this isn't a possibility.

Labman,

I thought about it being a 3 way but I don't think that it is. Most of my house has a switch controlling half of a duplex outlet but this switch really seems to control nothing. Any other thoughts? If I remove the switch, what should I expect to see if it's connected in series vs parallel? It's been a long time since my physics days.

Trying to install some track lighting so decided to do some investigating. There is a light switch in the room that controls nothing in the house. I've tested every outlet on the circuit and no change. Opened it up and see that there are 3 wires. One white, one black, one red. The black and red and screwed onto the right side terminals and the white is screwed into the top left. Testing the wires, both black and red are hot so it would appear that this switch is in the middle of the circuit. Examining the crawl space behind, I cannot see where the whiles lead. How can I determine what this switch was supposed to control? The majority of my house uses switched outlets and I would imagine someone just forgot to connect this one up. I would like to use this switch to control the new lighting so determining the outlet would facilitate this matter.
If there is 3 wires on the switch, that would be a 3 way switch.There should be another switch somewhere in the house.there is a switched outlet or receptacle in that room somewhere.You will just have to do some more searching to find it.I am an electrician and do a lot of troubleshooting.If that swtich is near a doorway and that room has more than one way to enter, check that doorway and that should be your other 3 way switch.Reply back if this helps.

Dos the switch have "ON & "OFF" on the handle? If so it is a single pole switch.

If there is no marking on the toggle handle, and it has three screw terminals, with two brass and one screw black or darkened, it is a three way switch.

If it is a three way, then there should be another three way switch somewhere. Is there another switch with no markings on the handle? If so, what does it control? It could be a 3 way for an outlet.