I installed a new, very bright, 50 watt LED floodlight over my garage door an set up an Appliance module to turn it on from dusk to midnight. The controller always turned it on after a few seconds of connect time.
This was a great solution to replace my ailing Metal Halide lamp over my garage door. The issue I ran into was that the X10 computer controlled lighting system would always turn on due to the behavior of the power supply in this LED fixture. X10 modules have a feature that allows you to trigger them on by cycling the controlled unit on and off twice. It turned out that the problem was an interaction between this feature and the Lamp electronics.
This feature can be disabled in an X10 "Appliance" module by taking the module apart and looking for the resistor and capacitor that allows a bit of AC current to flow to the appliance while in the off state. I disconnected these two components in the module and now the lamp stays in the off state until the system sends the on command.
JeffD