I wanted to change a toggle 3-way switch to the rocker one on top of the stairs but ends up the ceiling light is not working as expected, can't turn off at the other end (bottom of stairs) and then back on. I tried to connect the three wires (black, white, red) to different screws and had no luck. I found out actually the black wire is not from the same cable! Eventually I removed both switches and tested all the wires using a voltmeter and found out the black wire at the bottom switch box is a hot one, but the 'white wire' in the top switch box that connects to the black wire with a wire connector is HOT also. So which one is neutral? Is the power source come from the black in the bottom switch box OR through the light fixtures? I did not mess with the wiring in the bottom switch box (though I disconnected the wires, the black was originally attached to the black screw, the white and red were attached to the brass screws), hence I think the issue is in the top switch box. PLEASE HELP

 

At both switches connect the black wire to the COMMON screw. It's the black one.
Connect the red and white to the other two screws. It doesn't matter which one.

 

Thanks for your reply. Did you mean the black wire that was connected with a wire connector in the upper switch box should be disconnected from the other white wire? Where should the black and white wire of the two-wire cable in the upper box go to?

 

I went back and added labeling to your pictures. The C wires are the common ones.
The other two are travelers and can go on either remaining screw.

 

In each switch box you have a red black and white wire free and not connected to anything. The black goes on the common at both switches.
In one box you have a black and white connected. Leave them connected.

 

Thanks Joed and Pjmax for your help, it works !!. Not sure what I have done for the last several days since I tried different combinations...may be confused with the holes for the common push-in connection at the back of the switches. Out of curiosity and I know it is a dumb question, why the white in the upper box is hot? Is it the power source or the black in the lower box?

 

I recommend you don't use the holes. They are very common source of bad connections. Use the screw terminals.
The white is hot because it is being used in a switch loop. The white brings power to the switch and the black brings switched power back to the fixture.

 

Thanks for your time to reply and share your experience, really learn something new everyday.