I’ve encounter very bizarre behavior when replacing a very old three-way switch in my mother’s old house, and I’m trying to understand just what might be going on.
One light is controlled by two three-way switches. One switch wore out, causing the other to also stop functioning.
I replaced only the broken out three-way switch. Light works again! Except…
When the new three-way switch is up, the light is on. If I flip the second switch up, light flickers and remains on. Light only goes off when both switches are down. Same behavior with the second switch — if I turn the light on (switch up), flipping the replaced switch causes it to briefly flicker but still stay on.
Is this a wiring screw-up on my part, or are these three-way switches possibly not wired as three-way switches? I don’t know the behavior prior to the first switch being replaced, but I’m told it functioned “normally” before. Other older three-way switches in the house still behave properly.