I have 2 of the same fixtures. One by the front door, controlled by "standard" X10 dimmer switch, i.e. not a 3-way switch. The fixture has it's own motion sensor. This fixture has been in operation for over 5 years with no problems.
The other location is near the garage door and is controlled by a 3-way X10 switch, one inside the house and one in the garage. The fixture(s) in that location have failed 3 times in the same five years. Same model, same set up other than the 3-way switching. I should note that the switches rarely even get used, other than to set the initial brightness. The motion sensors do all of the hard work.
I know the fixtures themselves are bad because once they fail, they will not work even if wired directly to the power. In one case, I jumpered around the motion sensor and the bulb lit, so something seems to be frying the motion sensor portion.
Last night I unhooked the fixture and tested the voltage coming from the 3-way switches: 87V. That didn't surprise me since I keep the fixtures slightly dimmed. What did surprise me was that I could not adjust that voltage via the X10 switches. I did not have ready access to another fixture to use as a load for the X10 switches, so my testing ended there. I plan to hook something up tonight, but I'd figured I'd post my question anyway.
So, the first question is: Do the X10 switches need a load in order to dim/undim or should I be able to see the voltage change when I hold the button?
The second question is "Is it possible that I have simply gotten 3 bad fixtures in 5 years?" (That's not really a question looking for an answer, *of course* that could have happened.)
They are not expensive fixtures, but if they are that bad, I would think that the one by the front door - which gets activated way more times than the garage fixture - would have failed by now.