Could you give an explanation of this scenario? Maybe how to correct it? I have what sounds like the same problem. The switch at either end of the hall will turn the light on or off, but only if the switch at the opposite end is in the “correct” position. It’s been like this since buying this house 20 years ago. Although I have installed a 100 amp panel in my garage and run several 220 volt circuits, I still find electricity to be a mystery, and my eyes glaze over when looking at 3-way switch diagrams.

This sounds like a case of crossed travellers. On the switch that has to be in the “correct” position you’ll have to uncross the travellers. Pull out the switch (after cutting the power) and you see 3 screws, 1 brass colored and 2 silver colored. Disconnect and switch the two wire on the silver colored screws. This should do the trick.

I had to replace a 3 way switch once which was damaged. I bought one new replacement. Wired it according to the box instructions. Wound up with the same problem as you indicate. I kept changing wires around till I finally got it to work correctly. My advise ie to get two new switches and wire them according to the instructions.

Sounds like a bad switch or someone miss wired it. Three ways are fairly easy one switch has power coming in and two travelers (goes between the switches) the other switch has the power going to the light and the two travelers. Switches are fairly cheap buy two new three ways and install them leaving the wiring the same. If that does not work it is a matter of figuring out someone elses wiring which can be challenging.

Since you have looked at the switches and they appear to be 3-way switches, it is time to consider the wiring between the switches. It seems that your two switches are hooked up in a series circuit. There might be no traveler (also known as a jumper, usually the red wire) or it has come lose from a switch. I think that the jumper wire provides a parallel connection between the two switches in addition to the usual black wire. The jumper (red) or the black wire can carry the current. I would suggest turning the breaker off, pulling the switch out and seeing how many wires are attached to it. In your series circuit, if either switch breaks the circuit (light is out), the other switch becomes inoperable because of the break in the circuit. Also, if the light is on, either switch can break the circuit and turn the light out.

The easiest way to think about three way switches is that the switches do not have an on or off. It is simple a two position switch. If the switch is up it is making contact between one brass screw and the black screw and if it is down it is making a connection between the other brass screw and the black screw. When the switches are in the correct position current makes a circuit. The way I wire them if one switch is up and one is down the light should be on. If both are up or both down the light is off. This permit annal people to establish a routine where the switch they use the most turns the light on when up and off when down. This requires crossing the travelers or putting one switch in upside down.