Troubleshooting two 3-way switch setups

[jwelectric]

I have an issue...probably overlooking something easy.

i replaced 4 lights controlled by 2 three way switches. The issue is that one switch does nothing at all. The other works fine.
Could it be as simple as a bad switch or can I have wires crossed?

Thanks!

or can I have wires crossed

[firecap04@gmail.com]

That's helpful. Thanks

[jwelectric]

In order for a three way switch to work it must be wired correctly.

Each switch will have one screw that is marked with the word “common”. Sometimes this screw will be darker color than the other brass looking screws
The common screw will ALWAYS have either the supply (hot) or the switch leg (the wire going to the light). The common of one switch gets the supply while the common of the other switch gets the switch leg.

The other two screws are travelers between the two switches. There should never be anything connected to these screws but the travelers which goes from one switch to the other. They do not get pigtails of any kind nor are they wired to any other wire.

The neutral is always connected so it is not switched. I like to teach that the neutral goes straight to the load with wire nuts.

how about this

[firecap04@gmail.com]

That explains it for me. Thank you

[MeasureTwiceCutOnce]

(IGNORE THIS POST: Problem apparently gone) This one seems a mystery. Went to one of my empty rental properties where I was unaware of any previous problem, and noticed some lights not working. Tenant had turned one breaker off. I turned it on and that breaker controlled two 3 way switches in different rooms that control parallel lights on back patio. There's also a pigtail on what may be the feed (didn't test yet) which likely goes to a single pole in the same room as one of the two 3-ways (or perhaps a receptacle also). Problem is, with breaker on, patio lights stay on all the time no matter what combination is made with the switches (i.e., on, on, on, on). Had to turn breaker back off and haven't gone back to diagnose yet (travelers SEEM to be wired OK at quick glance), but is there an obvious solution here??? UPDATE: For no apparent reason, everything is now working properly. Tenant must have come back to do something, but it wasn't obvious. Anybody ever seeing an on/on/on/on condition is still welcome to reply.

[Amy Broderick]

This assumes two travelers between the switches.

Assign each switch a number.
With switch #1 & switch #2 down, light is on or off?
With #1 up & #2 down, light is on or off?
With #1 down and #2 up, light is on or off?
With #1 & #2 up, light is on or off?

In principle, with the answers filled in, the problem(s) can be pinpointed.

Test cases welcome. . .

Off
On
On
On

Please help!

[ActionDave]

You have a common and a traveller miswired somewhere in the circuit. Do you know where the power comes to the circuit first? At the light or one of the switches?

[Amy Broderick]

Thanks for the reply ActionDave! The power comes to switch #1 first.

[jal]

Here is mine
off
off
off
on

Switch 1 regular 3-way has the incoming hot wire - tested with a NCV detector
Switch 2 is a dimmer with 3-way
Tested the travelers with an ohm-meter - they are good

Before this replacement
Switch 2 was a dimmer where it only had two screws and a traveler and the common were connected to the same screw
Switch 1 was a regular 3-way
and the behavior was
off
on
on
on

what is going on?
thanks
JAL

[jal]

Continuing with the above : I put the old 3 way switch and a new 3 way switch (no dimmer)
I get
off
on
on
on

just more info any help appreciated
JAL

[jwelectric]

just more info any help appreciated
JAL

Anything other than this and the switch will not work

In order for a three way switch to work it must be wired correctly.

Each switch will have one screw that is marked with the word “common”. Sometimes this screw will be darker color than the other brass looking screws
The common screw will ALWAYS have either the supply (hot) or the switch leg (the wire going to the light). The common of one switch gets the supply while the common of the other switch gets the switch leg.

The other two screws are travelers between the two switches. There should never be anything connected to these screws but the travelers which goes from one switch to the other. They do not get pigtails of any kind nor are they wired to any other wire.

The neutral is always connected so it is not switched. I like to teach that the neutral goes straight to the load with wire nut

.