Trouble with three way switches

Question

My dining room has a box on each wall with a single pole switch (for exterior light) next to a three way switch (for dining room interior light) that I attempted to replace with new switches. After changing all four switches out, all of the lights (two exterior lamps, dining room, kitchen, hallway, and bathroom) go out when I flip the first single pole exterior light switch off. This switch has 3 black wires connected to it which I’ve identified as the exterior switch, exterior hot, and the third is carrying power to the other light sources. I’ve tried wiring it multiple ways but it’s gotten me nowhere. Does anyone have an idea as to why this one single pole switch is controlling basically all of the general lighting in my house? Not sure what I did wrong. Any help would be greatly appreciated. Thanks

Answer 1

First, don’t experiment i.e. trying random stuff “to see if that fixes it”. There are lots of combinations that will work and will kill you.

Second, you are quite close on identifying the wire’s operational roles. They are:

• Hot from supply (always measures hot)
• Onward power to other points of use
• Switched power to the light

If the first and second are connected, then the rest of your house will work. And they should always be connected no matter what you do.

What’s driving you up the wall is that you are continuing a sloppy practice someone else started, which is using the switch itself as a junction block for unrelated things. (I.e. the connection between supply and onward).

Very few switches even have provision for 2 wires on the line screw; that generally forces you into using a “backstab”, which is a bad idea all around.

You may be better off obtaining wire, nuts and the other kit required to make this a pigtail connection: join the two important wires (supply and onward) under a wire nut, so you are not using the switch as a splice, and then have a third short wire hop from the splice to the switch. This will also make the circuit more understandable for the next person. (Who might be you!)

I pigtail most of my stuff for a different reason, most of my connections are in awkward locations. It is easier to pigtail the outlet on a bench, then at the box simply whip together supply, onward and pigtail with a wire nut.