[Richo]

Hello electrical guys,

I recently wired up a 4-way switch in a basement. I found many diagrams online but found this one to the be the easiest to follow:

1. At the first 3-way switch, where the wires are coming from the panel, run a length of the 3-wire romex to the 4-way switch location. Now run another length of 3 wire romex from the 4-way switch location to the second 3-way switch location. Lastly, run a length of 2 wire romex from the second 3-way switch to the ceiling light.

2. Back at the first 3-way switch, wire nut the two white wires together. The black wire from the panel gets connected to the side of the switch with ONE screw. The black traveller wire gets connected to the top screw on the other side and the red traveller gets connected to the bottom screw. Wire nut the ground wires together along with a 6" piece of additional ground as the "pigtail." Connect the pigtail ground to the ground screw.

3. At the 4-way switch, wire nut the two white wires together. The black wire from the first 3-way switch gets connected to the top screw and the red wire gets connected to the bottom screw on the same side. The black wire heading to the second 3-way switch gets connected to the top screw and the red wire gets connected to the bottom screw of the other side. So you have a black and red coming in on one side and a black and red leaving on the other. Follow the earlier instructions for the ground wires.

4. At the second 3-way switch, wire nut the two white wires together. The black wire coming from the 4-way switch gets connected to the top screw on the side with TWO screws. The red wire coming from the 4-way gets connected to the bottom screw of the same side. The black wire heading to the light gets connected to the side with ONE screw. Do the pigtail trick one more time for the ground wires here. At the light, wire nut the black wires together, then the white wires together, and then the ground wires together.

So I followed the diagram and instructions exactly, and it didn't work. I double and triple checked all of the wires and I had it exactly as outlined above. So I revisited the internet and did some more reading and tried a few different wiring patterns at the 4-way switch location, and this is what ended up working for me (original diagram modified)

Does this make any sense to you why the first diagram didn't work but the second does?

The 4-way switch is not labeled in any way as far as what screws are paired together and they are all the same color.

Thanks for shedding some light on this. :wink:

 

[loyal]

Wow...I do remember seeing a 4-way with a couple of screws
that were colored black so you could tell them apart. But I could be wrong on that:boat:

 

[Jim Port]

Diagrams can be technically correct, but, may not match the actual internal wiring of the switch. Normally there is a wiring diagram on the box to show how the wires need to be paired.

 

[Yoyizit]

For the four way in your top diagram, label the terminals 1 (top left of the switch in the diagram), 2 (proceeding clockwise), then 3, then 4.

If there is no continuity between 1 and 2, flip the switch.
Now there should be continuity between 1 & 2 and between 4 & 3.
Flip the switch.
Now there should be continuity between 1 & 3 and between 4 & 2.
1 & 4 should never have continuity; same with 2 & 3.

It's a DPDT switch with two internal straps and only four of the six terminals brought out. Two of the terminals go to the switch wipers (1 & 4 or 2 & 3, there's no way to tell from the outside). The other two go to stationary terminals.

If the terminal screw colors are all the same, then the physical placement of each terminal on the switch housing may have meaning.

 

[goose134]

The first diagram shows all of the switch contacts wired in series. The internal switching does not work that way. I am not savvy enough to draw on the diagram to indicate how those switches are internally linked but the second one is correct.

 

[joed]

You can not wire three way and four way switches based on screw position. They will very according to different manufactures.

On a three way the common screw is the black one. It could be in any of the htree positions.

The four way will have two pairs of screws. One pair is probably gold and the other is silver. One pair could be black. They will not be green.

 

[220/221]

You have a 50/50 chance of wiring the 4 way switch terminals correctly. The wire pairs go top/bottom or side/side. I think, generally, it's one pair opn the top and the other on the bottom.

I believe that yours would have worked side to side, a variation on your inverted side to side.

I don't know why they don't mark ALL of them clearly.:jester:

 

[DragonInspector]

A lot of times the 4way switch integral operation is an X pattern.
What I mean is that when you hold that switch in your hand & you view the 4 screws, they switch-over like an X.

A B

B A


In one poistion the 4way switch connects A to A & B to B.
In the other position the 4way switch connects A to B & B to A (vertically as drawn in my reply here).

Hope this helps.

The 4way structure wiring is nothing more than a standard 3way structure wiring with a "cut" right in the middle where you place the 4way switch device.

 

[hayewe farm]

If the switches are shown upright, the 3 way switches should be wired so the travelers are on the side by side screws and the power on the first and load on the second should be on the screw with no screw on the opposite side. You should have a wiring sheet for the 4 way.
All 3 way switches follow this logic

The 4 way is then inserted in the center of the travelers.

 

[Richo]

You can not wire three way and four way switches based on screw position. They will very according to different manufactures.

This is probably a good explanation as to why the first diagram didn't work right. The instructions don't state anything about attaching a wire to the common terminal, but rather to the side with the single terminal. If I recall correctly, the common terminal on the switches I was using was NOT on the single terminal side.

You have a 50/50 chance of wiring the 4 way switch terminals correctly. The wire pairs go top/bottom or side/side. I think, generally, it's one pair on the top and the other on the bottom.

I believe that yours would have worked side to side, a variation on your inverted side to side.

This was the second variation I tried (black on one side, red on the other), and the 2 end switches functioned as a 3 way circuit would when the 4-way switch was in one position but the circuit was dead with the 4-way in the other position. The next step was swapping the 2 red wires on one side and that did the trick.

Using a continuity tester on the 4-way as yoyizit spoke of would tell me a lot about the internal wiring of that switch, but that means I would have to pull it out of the wall and disconnect it, not something that I'm too enthusiastic about doing. :no:

Thanks for all the input. That explains a lot.

 

[AllanJ]

OT: I don't think you can assume the location of the common screw on a 3 way switch either. Like the 4 way, you need to do tests if all of the screws look the same.

OT: Now that you found a 4 way switch where you need to connect one cable's conductors to diagonally opposite screws, that means that if you guess wildly you have a 1 in 3 chance of getting it right. (top 2 and side 2 being the other choices)