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[stanb]

Ten years after installation and satisfactory operation, two of my wall switches are suddenly turning lights on by themselves, even with the PHT04 X10 Pro timer disconnected. Both switches do respond to the settings in the timer, when it is connected. Both modules work by pushing their buttons. But they turn on again, at random time intervals after turning them off. I have tried all the tips I could find in these forums and nothing works.

I'm thinking the switches might be defective, but the fact that they work otherwise have me baffled.

Can anyone offer some help, please?

[dave w]

Yes. Make sure the bulbs are screwed tightly in their sockets.

[stanb]

Thanks for the suggestion. I tried that, but the problem persists.

(and you don't look fat, from here in California)

[JeffVolp]

There have been several reports of powerline noise doing exactly this.  It is possible for multiple noise sources to sum together in such a way that they can emulate a valid X10 command.  And, I have witnessed noise morphing one X10 command into another.  This report includes a photograph of a simple cellphone charger generating noise that the ESM1 signal meter believes is a "GOOD" X10 code:

http://jvde.us/x10/x10_cellet_noise.htm

Jeff

[Dan Lawrence]

Just out of curiosity, Jeff, what cell companies in the US/Canada use this type of charger?  Our cell phones are from Verizon and no oddball signals result from their chargers, one is plugged into the same outlet as two lamp modules with zero noise.

[JeffVolp]

I believe most "wall warts" contain switching supplies today.  Whether they interfere with X10 control depends on the frequency of the switching supply, and if they include a filter network to prevent that noise from reaching the powerline.  I have had communications with a number of people who identified a cellphone charger as a noise source in their installation.  I don't know what brands they were.  None of the Verizon chargers used here appear to cause any problems either.

The charger in that report was sent to me for testing by one of my customers because it raised havoc with his system.

Jeff