# Light switches

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• posted on November 6, 2009, 3:35 pm

I have an L-shaped hallway with:
a ceiling light in the middle of each leg a light switch at the end of each leg a light switch at the intersection.
Several years ago, I used to be able to turn the lights on and off from any switch. But now the lights can be turned on and off by only one switch (at the end of one leg).
In previous attempts to resolve this problem, I replaced all of the switches but I didn't record what wires went to each terminal.
Question: What kind of new switches do I need (single-pole, 3-way, 4- way) and how many of each?
How do I determine what wire connects to each terminal of each switch?
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<%-name%>
• posted on November 6, 2009, 3:52 pm

You need two three way switches and one four way (or you can use three four way switches and just disregard one terminal on each.)
To determine how to hook them up, you'd have to open up all the boxes and puzzle out the wiring. There's many different ways they could be hooked up and it is difficult to determine from here which you have :)
nate
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<%-name%>
• posted on November 6, 2009, 5:19 pm
wrote:

You need two three way switches and one four way (or you can use three four way switches and just disregard one terminal on each.)
To determine how to hook them up, you'd have to open up all the boxes and puzzle out the wiring. There's many different ways they could be hooked up and it is difficult to determine from here which you have :)
nate
You can't use a four way as a substitute for a 3-way. There's no common terminal on a four way switch.
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<%-name%>
• posted on November 6, 2009, 5:34 pm

Sure you can; any of the 4 terminals can be the common, with the travelers connected to the opposite 2 (and the one directly across unused).
To the OP, you need to continuity-check the wires to figure out which ones are the "travelers" -- these go between the switches only. The original 3-way switch locations will have 2 travelers, the 4-way location will have 4 travelers (2 each connected to the 2 at each 3-way location).
Google "4 way switch diagram" and you'll find more information -- there are many ways to run the physical wires, but they all degenerate to the same switching flow.
Josh
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<%-name%>
• posted on November 6, 2009, 6:12 pm
wrote:

Josh,
How? if you number the terminals on a 4 way as 1 through 4, the hot ones are 1 and 3 when the switch is in one position and the hots are 2 and 4 when the switch is in the other position. There is not one terminal that is 'common'. If there's no common, then you don't have a terminal that goes from the switch to the fixture (or, for that matter, there's no common for the originating hot). If I'm misunderstanding this, please help me out.
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<%-name%>
• posted on November 6, 2009, 6:31 pm

The 4-way switch just passes through or crosses the wires from one side to the other, depending on position. Putting 1 and 2 on the top, and 3 and 4 on the bottom of the switch:
Switch down: 1 <-> 3, 2 <-> 4 Switch up: 1 <-> 4, 2 <-> 3
So to use as a 3-way, use terminal 1 as common, 3 and 4 for the travelers, leaving 2 unused
Switch up: 1 <-> 3 Switch down: 1 <-> 4
Which is exactly what a 3-way switch does (and you can start from any of the terminals as common, with the 2 furthest away for the travelers).
Some diagrams of 3 and 4 way switch wiring:
http://www.ezdiyelectricity.com/?page_id81
Josh
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<%-name%>
• posted on November 6, 2009, 6:41 pm
wrote:

In every instance in the diagrams you posted, there is no terminal that is always 'in use' on any of the 4 way switches. There is no common.
In this diagram:
http://ezdiyelectricity.com/images/wiringdiagrams/receptacles/3-way-split-receptacle-diagram-600x420.jpg
the terminals (1 & 2 on top, 3 & 4 on bottom), the terminals used are either 1 and 4 (top left and bottom right), or if the switch is thrown, 2 & 3 (top right and bottom left). which terminal is the common?
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<%-name%>
• posted on November 6, 2009, 6:47 pm

That's because the diagrams are only showing one position of the switch (crossed); when the switch is in the other position, the switch connects the top 2 terminals (in that diagram) together, and the bottom 2 terminals together. That makes any of the terminals common to the 2 terminals opposite it.
This set of diagrams shows the actual operation of the circuit better:
http://www.wfu.edu/~matthews/misc/switches/4WayStills.html
Josh
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<%-name%>
• posted on November 6, 2009, 6:54 pm
wrote:

Josh,
thanks.
jc "a man is never so sure he's right as he is the moment before he's proven wrong"
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<%-name%>
• posted on November 7, 2009, 4:05 am

I didn't see it at first but Josh is right. You can use a 4-way for a 3-way.
1 2 1 2 X 3 4 or 3 4 .
In one position 1 conects with 2 and in the other it connects with 4. Don't use 3 and the remainder of the switch is like a 3-way.

No, your description is wrong here. In one position it is 1-4 and 2-3. If the wsitch is thrown, it's 1-3 and 2-4. Either 1 or 3 (but not both) can be used as the common. 2 and 4 are meant for the travelers.
Oh, I see you agreed a couple posts down.
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<%-name%>
• posted on November 6, 2009, 6:43 pm

a three way switch is a single pole double throw (S.P.D.T.) switch: input A, outputs B and C Switch up: A connects to B Switch down: A connects to C
a four way switch is a double pole double throw (D.P.D.T.) switch with a cross connected internal connection:
inputs A and B. Outputs C and D Switch up: A connects to C, B conects to D Switch down: A connects to D, B conects to C
To use a 4 way siwtch as a 3 way switch, leave one input (B) unconnected. UP: A connects to C. Down: A connects to D.
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<%-name%>
• posted on November 6, 2009, 6:47 pm
wrote:

clarifying.
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<%-name%>
• posted on November 7, 2009, 6:49 am

These switches don't connect to the hot or the load they connect to the travelers.
There are 4 terminals lets call them A, A+, B and B+ In one position A is connected A+ and B is connected to B+. In the other position A is connect to B+ and B is connected to A+. Think straight thru or crossing over. Draw a diagram of a 3 way switching circuit and insert this switch between the two switches connected to the travelers. Follow the current path as you change each switch. Draw it out, work thru it until you understand it and tyou will never forget it. Changing the position of the 4 way switch has the effect of reversing the connection of the travelers on a 3 way switch. You can have as many 4 way switches between the 3 way switches as you like. My inlaw's house has a circuit with 4 four way ans 2 3 way switches to control a light in the den
BTW in a pinch you can use a 4-way switch as a 3 way switch. let A or A+ be the common and B and B+ will be the travelers Also if you choose B or B+ as the common A and A+ will be connected to the travelers. Jimmie
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<%-name%>
• posted on November 6, 2009, 5:20 pm

I'm counting only 2 switches. I had same problem and learned that you have to replace exact wires on switch when you replace a switch.
I kept playing around with it and finally an electrician with his meter figured it out for nothing as he was making an appraisal on another job for me.
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<%-name%>
• posted on November 6, 2009, 6:47 pm

I used to live in a house that I was renting from a guy who had "updated" the electricals (translation: he had replaced the switches and receptacles.) Unfortunately he wasn't real careful wiring up the three way switches, and to make matters worse, the house had old cloth covered wiring which meant that all the wires were a dirty brownish- grey color :)
I figured out how to make the hall lights work properly in an afternoon, but it's one of those things, I can *do* it but God help you if you want me to show you *how.* Worse yet if I have to do it over the Internet...
Probably the easiest thing is to pull everything out of the wall, disconnect everything, and first identify which wire is still hot (after you turn the breaker back on, because you turned it off before you started, right? RIGHT?)
From there, hopefully everything will be self evident (pay special attention to which individual wires come from which cables) but if not, either hooking up a 3-way at the "hot" location and continuing to the other locations and/or using a 9V battery and a test light can help trace out what goes where.
good luck
nate
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<%-name%>
• posted on November 6, 2009, 9:39 pm

Whenever a system like this craps out, the problem is invariably the 4 way switch. They just don't seem to be made as well as single poles or 3 ways, possibly because of it's switching complexity. For this reason I wouldn't advise using a 4 way anywhere that it's not required. It's also more expensive

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<%-name%>
• posted on November 6, 2009, 9:49 pm

Hmm, I found an old snappy style 4-way at the base of the stairs when I replaced it (could have been a three way, but apparently builders used a 4-way because that's what they had;) the only reason I replaced it was that the girl didn't like brown switches. It appears to have been there since the late 40's. I still have it in my junk box...
or is this one "don't make 'em like they used to" kind of deals?
nate
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<%-name%>
• posted on November 6, 2009, 10:00 pm

Hmm, I found an old snappy style 4-way at the base of the stairs when I replaced it (could have been a three way, but apparently builders used a 4-way because that's what they had;) the only reason I replaced it was that the girl didn't like brown switches. It appears to have been there since the late 40's. I still have it in my junk box...
or is this one "don't make 'em like they used to" kind of deals?
nate
You can buy good switches today, but back in the forties, I don't think you could buy crappy switches. I think that because it's a complex switch, it is more vulnerable to failure. What I can say for certain is that whenever I'm diagnosing a malfunctioning multi-switch system, the bad switch is invariably, the 4way.
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<%-name%>
• posted on November 7, 2009, 4:18 am

This would also be a good clue where the problem is!!! :)
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<%-name%>
• posted on November 6, 2009, 11:20 pm
On Fri, 6 Nov 2009 07:35:03 -0800 (PST), gcotterl

Take all three switches loose and find the only hot wire in the bunch. Put a 3 way there. Finished (The hot goes to the common)
Go to the 4 way and find the two wires the first switch makes hot when you switch it back and forth. Put a 4 way there with those two wires hooked to the same color terminals on the 4-way Finished
Go to the last 3 way and find the wire that does not get hot when you flip the other two switches. Put that wire on the common of the last 3 way. Finished
Miller time