I wired our house when we built it. We have had one 3 way that has never worked right. It is one of two in the house I had problems with. Because of where it was we rarely used but one switch and it worked fine. Today I was installing missing cover plates and one outlet that had never gotten installed, the small stuff that if you not careful never gets done. One of my goals was to fix that switch.
Before when this has happened it has always been that I got two wires reversed so I assumed that to be the case here. I looked over the circuit and thought I saw the problem. Fixed it, turned the power back on ... nope! OK try again. After about an hour and a dozen trips back and forth form the fuse panel I finally accepted the fact that I had no idea what the heck was going on!
I went the truck and got my meter and started testing. Obviously there was something not right. Power was where it was supposed to be and I now I was totally stumped. Finally just pulled the switches out and decided to start from scratch. I checked the switch to make certain it worked like I thought it did. Guess what I found? A bad switch! That is why I was having so much trouble. Scrounged around in the box of electrical stuff in the Lab and to my surprise there was a new 3 way down there. Replaced the switch and it still didn't work.
Talk about ready to pull you hair out! Good thing was it turned out to be the same mistake I make every time. I reversed two wires and FINALLY everything worked like it should. I think I spent close to two hours on that stupid switch and walked about a half a mile back and forth from the fuse panel.