I'm puzzled, hoping someone can explain this. I've been gradually finishing a bonus room for a year or so. Late last year I installed recessed lighting and a ceiling fan. I'd previously run a 20A circuit to the room for a microwave, but ended up using it for the ceiling when my plan for the room changed. Everything worked, but the fan turned at half speed - slow was slower, fast was only medium. I'm 99% sure I wired it correctly, I checked all the connections, and the lights are fine. Other stuff happened, and it got put on the back burner. This spring, I put a sub-panel in my garage to add 220 and a couple 20A circuits. While doing that, I swapped that 20A breaker for a 15A, since no need to run 20A just for lights and a fan. Well, lo and behold, my fan spins at full speed now, and a voltmeter shows full voltage at the switch and the fan. Don't get me wrong, I love it when problems solve themselves, but I sure would like to know why. Anybody have an idea?
) a breaker with a higher rating should have less impact because the electromagnet is weaker so that it won't cause the switch to throw (opening the circuit) until more power is passing through it. Neither breaker should cause much power loss. I think Tim is on the right track though - something is wrong with the old switch. I would toss it out.