I want to replace one 3 way switch with a dimmer. The line power goes to the first switch and then to the other switch and then to the lights. When I replaced the first swtich with the dimmer it didn't work correctly. The 3 way dimmer has 2 black wires and one red wire (and a ground). I attached the wires as per the old switch (red to red, black to black etc).
I can't figure this out.