Electricians: Four-Way Switch Help Needed

Factual Questions
1

I have a four-way circuit controlling a single light fixture. There are three switches, two three-way and a four-way. The power enters from a three-way switch (let’s call this S1). S1 is also connected to the light fixture. S2 is a four-way switch that is connected to S1 and S3. S3 is a three-way switch that is connected to S2. I believe all three switches were working as they were supposed to.

All three switches look old. I would guess they were 30-40 years old. A week ago, S3 started making arcing noises when it was turned on. So, I replaced S3 with an new three-way switch taking care to ensure the wires went to the same terminals on the new switch; black to the common (which was black on the new switch), red and white to the other two terminals. The arcing noise has stopped with the new switch.

After doing this the light will only turn on with certain combinations of the three switches. If S2 (the four-way) is used to turn the light off, neither S1 nor S3 can turn it back on. S1 also must be in one position or S2 and S3 can turn the light on.

I have replaced the other two switches and have checked them with an ohmmeter. They all work as they are supposed to. So, all three switches seem fine. I’ve also checked all the connections and they seem good.

Anyone have any idea what could be wrong?

2

The short answer is that if everything was working correctly prior to your replacing the switches, then you either misconnected one of the three way switches (the four-way merely flips travelers), or you managed to disturb a wire nutted connection in one of the device boxes.

First you said you replaced S3. Did everything still work correctly before S1 and S2 were changed? If you did evaluate after each device changeout, then that could narrow your troubleshooting focus.

3

Switch the two travelers in the switch you replaced. Should fix the problem.

4

Thanks for pointing out the problem must be in the wiring of S1. So, I checked the new and old switch. The old switch did not have common labeled. It turns out the common terminal was the one on the side by itself. On the new switches the common terminal was one of the two together on one side. I was wiring the new switches by carefully moving the wires to the corresponding locations on the new switch. This reversed a traveler and the common.

So, I reversed the wires and put the wire which was on the common on the old switch on the common on the new switch ignoring the physical locations. Everything now works.

Thanks for the help. This really did help me solve the problem.