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Three way switches

Three way switch wiring can sometimes get confusing. If you are wiring or replacing a 3 way switch, and it is not working quite right, you probably got a wire mixed up.
The proper way to wire the switches is to run a 4wire cable between the switches. That is black, white, red, green.
In all electrical installations, the green wires are interconnected and also pigtailed and connected to the metal wall boxes and to the green screws on switches, receptacles, or lights.
On the 3 way switches there are a pair of like colored screws, usually brass. These are for interconnecting the switches. The red and black of the 4 wire cable connect to these terminals at each switch.
The other wires are connected in different ways for differebnt situations. Look at these sketches for cases where the cables for the light and power are in separate wall boxes..

and for when the light and power cables are in the same wall box..

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3 way switch diagrams

Three way switch diagram: Three-way switch has 3 screws


Before replacing old 3-way switch, mark the wire connected to dark-colored screw
Connect that wire to dark-colored screw on new switch.

If you are confused which wire goes to dark-colored screw
Mark the 2 black wires and the red wire.
You are not going to do anything with the white wire.
Connect blacks and red to any screw, turn on power, and try BOTH switches
Keep trying until correct combination is discovered
Both switches must work in all possible up-down positions before wiring is correct
Incorrect wiring will not blow circuit breaker, the circuit just doesn't work until wires are right.

Four way switch is added to 3-way circuit


Oct 09, 2010 | Garden

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Look carefully at the box you got the switch out of.

A 4 way circuit normally sits between two three way switches. The 4 way makes and breaks the wires that ONLY travel between the two 3 way while the third wire on the three way is "line" or "load"

Since you are replacing an existing set of switches, pay attention to the terminals of the devices you are removing. You will see that the screws on the terminals have distinctive colors. Hook them to the new switches the same way.

Again, look carefully at the diagram thaat is on or inside the box

I hope I have not confused you with this explaination.


Oct 17, 2009 | Electrical Supplies

1 Answer

While driving went to flash lights and the whole car quit. No power whatsoever - only seat adjustment switches work. When turning the key .... nothing at all. What could this be?

Two or three times in my life I've encountered this. I'm not a mechanic but I've been told it's called the 'feed wire' which is a little wire that runs off the negative battery cable right where it connects to your negative battery post. It will sometimes get broken or rusts through and is shorting out by contacting metal etc., and this basically shuts off power to every system in the car. I have solved this for myself and others by simply fixing the little wire, which is pretty easy and open. 
I'm confused about why your seat switches would still have power. In the 'feed wire' cases I've solved it's always the same thing, people diving down the road and suddenly EVERYTHING goes dead and the car stops running. 
Hope this helps

Jul 04, 2009 | 1986 Lincoln Town Car

2 Answers

Compressor problem, installing the Supco 3-in-1 Relay

Hi, If the 3 posts are top center and bottom right left, the black wire goes top the top center post. The red wire will go to the bottom right and the white goes to bottom left.
If the posts are bottom center and top right left, the black goes on bottom center and the red goes top left. The white goes top right.
If you do not see a capacitor, disregaurd the wires in the 3-1
I hope this helps you. Please let me know if I can assist you further.


Jul 02, 2009 | Maytag SkyBox MBV1976A Beverage Dispenser

1 Answer

Replacing a relay switch/kit on a maytag refrigerator MSD2432GR

Wow! I am confused also. It sounds like it is more complicated than the ones I use. Can you send me an image of the relay and the terminals on the compressor?
I can tell you that the live wire ( wire with electricity) is the one that goes on the common terminal, that is the one that it at the top of the trangle formation, unless the formation is upside down then it goes on the bottom. Then the other neutral wire goes on the run terminal which is usually on the right if the triangle formation is right side up. Usually the neutral wire is white. So
try putting the white wire on terminal 3 and the orange on the top (or bottom) terminal. If there are any wires left over that you think need to be connected I would need to see an image.

Dec 05, 2008 | Refrigerators

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