3 Way Switch Wiring Diagrams
In all these
diagrams you will
not see a ground
wire. It is only left
out to avoid
confusion. This
doesn't mean it is
not important, it is.
Be sure every box,
device and fixture
is grounded. If you
have a situation
that I have not
covered here,
contact me and I
will try and help.
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this in PDF format

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3 way switches can be one of the most confusing
aspects of wiring. One reason is the numerous ways
a 3 way switch can be wired. I created this page to
help you troubleshoot that 3 way switch in your
staircase or hallway. Clear easy to read wiring
diagrams. The diagrams show several different wiring
configurations in schematic format. If you are
interested in more troubleshooting tips, visit my tech
Troubleshooting 3 way and 4 way switches with
wiring diagrams
I do not recommend anyone other than a qualified electrician
perform any electrical work. This is for information purposes
only and for understanding how this type of electrical system
works. If you choose to do electrical work be sure to turn the
power off.
Electricity Kills!
It is very important to first understand exactly how a 3-way system operates. If you
follow the simple line drawing above you can see that by following the solid line
from the hot wire all the way to the light it makes a complete circuit.

The solid line in the switch represents the switch being in one position while the
dotted line shows the alternate position the switch can be turned to. You can see by
flipping either switch the circuit would open and the light would turn off.

This is a simple schematic and does not show how the actual wires would run. I will
show some of those in the following diagrams. In some cases there may be more
than 2 locations to turn on a light or lights. When 3 or more switches turn on the
same light or lights a 4-way switch is required.
In the wiring diagram above we can see the 4-way switch installed between the two
3-way switches. You can put multiple 4-way switches in between two 3 ways.

Notice in this diagram you can see the actual operation of the switches. The solid
line is the actual switch position while the dotted lines show the alternate position.
With a 3-way switch system there is a number of variables that make
troubleshooting very difficult for a novice.

The most common mistake is made when a switch is simply replaced. The
common screw on a 3 way switch has to be connected to the proper wire or the
system will not work correctly. The basic premise is always the same.

In the diagram below you can see one common is the hot wire and the other
common goes to the light. It doesn’t matter on which switch these go but they must
go to the common screw. On most 3-way switches this is the black screw with the
other two screws being brass colored. The two traveler wires go only from one
switch to the other. It doesn’t matter which of the two screws they go to on each
switch as long as it is one of the 2 brass colored screws.
Do you understand the basic concept? If not I can explain it this way.

Sometimes, to make it easier to visualize how this works, try to imagine the
simple wire diagram as a series of pipes. In order for the water to flow through the
pipes they must all be connected so the water can flow from point A to point B.
The switches are valves that prevent or allow the water to flow.

Now the confusion generally comes when you remove the first switch and see 7
wires in the box. You have to keep in mind there are a lot of combinations when it
comes to wiring a set of 3-way switches and they will all work properly. For that
reason it is very important that you first understand the basic theory as seen in the
above diagrams before you can troubleshoot the system. Let’s look at some
In this case we have the 2 wire feed, the 3 wire cable going to the other 3-way
switch as well as the 2 wire cable going to the light, all in the first box. The second
switch box has just one 3 wire cable and the light box has just one 2 wire cable.

In most cases when a 3 wire is used from one 3 way switch to another you will find
the white is used as the common. This has been a standard practice for years. A
piece of black electrical tape denoting the white wire as hot is a good idea here.

In the first box notice the neutral or white from the feed is spliced to the neutral or
white from the light. The black or hot from the feed is spliced to the white on the 3
wire cable. The red and the black on the 3 wire cable are the travelers.

One important thing to remember. Never assume anything when it comes to
electrical wiring. The wiring may not have been done properly and things may not
be what they seem. Many times i have seen the neutral used as the switched wire,
meaning at the light, even with the switch off, the wire at the light is hot all the time.

Always use a voltage tester to check which is which. On that note always make sure
your tester is working on known live circuit before assuming that it works, they do

Okay let’s look at another scenario. Onto the
next page >>>
(C)Copyright 2005 Forte Electric Inc.
Forte Electric
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Three way and four way
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