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I have a metal junction box in the kitchen of my 1968 home. This jbox contains 2 lights switches that I want to replace. enter image description here

One switch is a 3 way that is for the overhead light/fan that can also be turned on/off by another switch. That had one common wire that was yellow and 2 blue wires. I just wired the new switch exactly as the old and it’s working correctly. enter image description here

However, I thought the seconds switch would be a single pole because it only turns on an outside light. I bought a single pole that has 2 terminals. Unfortunately, when I pulled out the single pole switch it has 3 wires. 1 yellow which I believe is the common wire, is in a push-in on the back and 2 red wires. One of the red wires is in a push-in and the other is on the terminal.

So, do I need a different on/off switch because I don’t know how to get 3 wires on a switch with only 2 terminals, no push-in. I sincerely appreciate any advice you can give me.

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    In the case you describe the switch contact is being used to connect two wires and not to provide a certain function like the third wire on a 3-way switch. The yellow on this simple switch is not called a "common". A simple switch has a line hot wire attached to one contact and a switched hot to the other. A 3-way switch has one contact called the "common" but a wire connected to the common is not called the common wire. Jul 31 at 11:31
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    One of the two red wires is probably the line hot and the other is a short piece of wire going to another switch in this same box. Is that what you see? Jul 31 at 11:41
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    I used the word probably above because there is another possibile reason for having two wires connected to one terminal of a simple switch. That other reason would be if this one simple switch were controlling two different light fixtures. What is your arrangement? Jul 31 at 12:17
  • The 3 wires coming from the single pole on/off switch seem to be as follows: one red wire is going up through the box through the galv conduit on the left side, that would probably be going to the light fixture outside. The other red wire is going through the conduit on the bottom of the box, there is a lower outlet near there. The yellow wire goes up the conduit on the right side of the box.
    – Emmeline
    Jul 31 at 15:33
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    Then more investigation would be needed to determine which of the three wires is the line hot, but this is not necessary to reconnect to the new switch. As the answer says connect the two red wires to a short piece of wire and connect the other end to one terminal ofvthe switch. Connectbthe yellow wire to the other contact. Easier still would be to connect both red wires to the same contact, if the new switch allows that. Jul 31 at 20:45
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The two reds are connected together internally in the switch. This usually is done to daisy chain the hot to another device, but it could be separate feeds to multiple lights.

The most universal answer is to get a +/-4" piece of solid wire (not white, green or gray) to connect to the new switch, then connect that wire and the two reds together with a properly sized wire connector.

Alternately if you have a switch with terminal plates (like this receptacle) enter image description here
you can lay one wire on each side of the screw under the clamp. (Those wires are stripped back a little too much.)

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    I think I’m starting to understand. One red wire brings power to the switch and the other takes it on to another receptacle. So, are those both hot wires? This ties in to what I’ve seen in some of the other outlet receptacles where I didn’t find a single cut wire under the terminal but one long wire with the coating removed at the terminal point where it connects and loops around. Wouldn’t that be the same idea? Powering the outlet and then going on to another.
    – Emmeline
    Jul 31 at 21:06
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    So i have 2 options:1) buy a 4” length of 14 ga. Insulated copper wire, any color except white, green or gray. Connect that wire to the terminal. Then pigtail the end of that wire with the 2 red wires that were previously on the old terminal and cap them with the proper sized electrical nut and stick them in the box. Or 2) connect both ends of the red wires to the same terminal, one on each side. With either option I would have yo connect my yellow wire to the other terminal on the switch. What is the yellow wire? On outlets I’ve mostly seen red and white wires.
    – Emmeline
    Jul 31 at 21:07
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    If the old switch worked, then this should too, even though you do not know what the various wires are connected to. It would be better to know, but if you don't have test equipment this is a semi-reasonable way to proceed. Jul 31 at 21:35
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    @Emmeline for clarity Re: "Or 2) connect both ends of the red wires to the same terminal, one on each side", as far as I know you can only do this if there is a plate (essentially a square washer) behind the screw head. Aug 1 at 13:46
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    And finally re:"one long wire with the coating removed at the terminal point where it connects and loops around", I had one particularly ornery inspector give me grief about that method not being included in the installation instructions, so he claimed he could ding me. He didn't, but warned he would in the future. Aug 1 at 14:13

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