I was replacing outlets and switches in my living room. The last switch I came to was for an outside light. When I removed the switch plate there were 3 black wires, no white or ground. Two of the wires plugged into the back of the switch and the other attached to a side screw. I attached one wire to the top side screw on the new switch and the other two to the other side screw. Now the outside light is on all the time and the switch turns the two outlets in the room on or off. Whats up?

  • I'm assuming that the wires plugged into the back, were one at top and one at bottom of the switch. Was the wire on the side screw at the top or bottom of the switch? Are the lights controlled by this switch, controlled by any other switches as well (3-way)?
    – Tester101
    Jan 28, 2016 at 22:10
  • Can you get us some photos? Jan 29, 2016 at 2:56
  • Were they plastic coated wires or fabric wrapped wires? I ask because fabric wires are sometimes entirely black except for one small line of a different color (red or white). Jan 30, 2016 at 18:32

1 Answer 1


Sounds like you removed a 3 way switch and replaced it with a single pole switch.

If the old switch does not have on/off marked in the handle and it has three terminals it is a three way switch. You need to replace it with the same kind.

One of the wires is either the hot feed from the panel or it runs to the light. The other two wires are travelers running to another switch somewhere.

  • I thought this might be the case as well, but I'm not sure it is. It could have been a single pole switch, where the installer used the back-stab and screw terminal to avoid a pigtail. Without more information from the OP, it's hard to say for sure.
    – Tester101
    Jan 28, 2016 at 22:58
  • That sounds like another good possibility with the limited information given.
    – ArchonOSX
    Jan 29, 2016 at 20:24

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