i recently changed three switches that control a ceiling light. i replaced them with two 3-way switches and one 4-way switch. the switches work at times depending on which switch i used last. for example, if i turn off the light with one switch, i can turn it off using a different switch. however, i can't turn it back on unless i use the same switch that i previously turned off with. there are four wires that come out of the wall to the 4-way switch and 3 wires for the other two 3-way swicthes. does anyone know how i can fix this problem without contacing an electrician? also, is my problem limited to the wiring for the 4-way switch only?

 

It is easy, but time-consuming, to fix this. You incorrectly attached the wires to the switches.

The bad news is that your problem is not necessarily limited to the 4-way switch. The good news is that no special skills are required to fix this -- all it takes is trial and error. The bad news is that there are 864 possible combinations (six ways to connect the first 3-way times 24 ways to connect the 4-way times six ways to connect the second 3-way). The good news is that many of these combinations are functionally equivalent (e.g., reversing the travelers on a 3-way makes little difference). So practically speaking, there are far fewer combinations.

Before we start, I want to make it clear that we don't do any experimenting at all with the grounding wires. The grounding wires go to the green screw on each switch. No place else, and no other wires go to this screw.

Start by shutting off the breaker.

Look carefully at one of the 3-way switches. Learn to identify which screw is the "common". It will usually be a screw that is black in color, and/or marked "com" or "common" on the back of the switch case. Now look at the three wires coming from the box. Once you pick one of these wires to attach to the common, it doesn't make any difference which of the other two wires goes to the remaining two screws. This reduces the possible combinations from 864 to only 216. Things are looking up already.

Pull the 4-way switch out of the wall and disconnect the wires. Look at those four wires in the box. The four wires you have are in two pairs -- you need to figure out how they are paired. You can pair the wires up by looking for wires that come from the same conduit or cable. Now look at the back of the 4-way switch itself. You'll see that the screws are in two pairs also. These two pairs are usually identified by the words "input" and "output" on the back of the switch, and/or they may be paired up by screw color. Now all you have to do is connect one pair of wires to the "input" screws and one pair of wires to the "output" screws. It doesn't matter other than getting the pairings right. This reduces the number of combinations from 216 down to only 9! Now we are getting somewhere!!

So start by connecting the 4-way as described above. We will not further mess with that switch.

Now get organized. At each switch, label the wires "A", "B", and "C" (or just refer to them by color if they are distinct colors). We'll call the two 3-way switches "1" and "2".

Here are the 9 combinations we need to check:[list=1][*]Switch #1, wire "A" to common. Switch #2, wire "A" to common.[*]Switch #1, wire "A" to common. Switch #2, wire "B" to common.[*]Switch #1, wire "A" to common. Switch #2, wire "C" to common.[*]Switch #1, wire "B" to common. Switch #2, wire "A" to common.[*]Switch #1, wire "B" to common. Switch #2, wire "B" to common.[*]Switch #1, wire "B" to common. Switch #2, wire "C" to common.[*]Switch #1, wire "C" to common. Switch #2, wire "A" to common.[*]Switch #1, wire "C" to common. Switch #2, wire "B" to common.[*]Switch #1, wire "C" to common. Switch #2, wire "C" to common.[/list=1]So proceed as follows:

• Make sure the breaker is shut off.
• Pick one of the 9 combinations above and wire it up.
• Turn on the breaker and test. See below for the set of twelve tests you need to do each time.
• If all twelve tests pass, you're done.
• If not, cross that one off the list and go back to the first step.

Here are the set of twelve tests you need to conduct after each of the nine experiments:[list=1][*]Switch#1 down, Switch #2 down. Verify that you can turn the light on and off with switch #3.[*]Switch#1 down, Switch #2 up. Verify that you can turn the light on and off with switch #3.[*]Switch#1 up, Switch #2 down. Verify that you can turn the light on and off with switch #3.[*]Switch#1 up, Switch #2 up. Verify that you can turn the light on and off with switch #3.[*]Switch#1 down, Switch #3 down. Verify that you can turn the light on and off with switch #2.[*]Switch#1 down, Switch # 3 up. Verify that you can turn the light on and off with switch #2.[*]Switch#1 up, Switch #3 down. Verify that you can turn the light on and off with switch #2.[*]Switch#1 up, Switch #3 up. Verify that you can turn the light on and off with switch #2.[*]Switch#2 down, Switch #3 down. Verify that you can turn the light on and off with switch #1.[*]Switch#2 down, Switch # 3 up. Verify that you can turn the light on and off with switch #1.[*]Switch#2 up, Switch #3 down. Verify that you can turn the light on and off with switch #1.[*]Switch#2 up, Switch #3 up. Verify that you can turn the light on and off with switch #1.[/list=1]

 

You will have to figure out which wire is which in the switch boxes. The hot wire should go to the black screw on 1 of the 3 way switches. On the other 3 way switch, the black wire that goes to the light fixture should be on the black screw. See the following image from homewireingandmore.com