x10 wireless remote switch stopped working

[TBolyard]

I have an exterior lighting circuit that is split off my garage circuit and (was being) controlled by X10 Wireless switch modules, but has stopped working recently.
 
There is a XPFM Inline Receiver module that is wired into the circuit which (as I understand it) gets a voltage change signal through the wires from a Mini-Transceiver (model TM751).  This transceiver in turn gets its signal from a model SS13A "3 Unit + Dim RF Style Switch".  This arrangement has been working for several years, but for the last several months it has been only working intermittently.  Sometimes I have trouble turning the circuit on, sometimes trouble turning it off, but it has always started working again within a few hours.  Suddenly, it has stopped working completely, with the circuit on.  I've tried turning off power to the garage, testing with an alternate SS13A wall switch, and testing with an alternate Transceiver Module (I bought a few spares and never got them installed elsewhere). This leaves me thinking that the XPFM Receiver has failed, but I don't have a spare.  
 
Any ideas on how to test this? 
 
I know these devices are several years old now. If I need to replace something, should I start from scratch with a new solution? What do you recommend? 

 

[RAL]

The XPFM responds to X10 power line commands, which in your case come from the TM751.   You should be able to test the XPFM with any other X10 wired controller, such as a WS467 wall switch or a mini controller, etc. 
 
X10 components are still available at reasonable prices, so if it does what you need, I wouldn't abandon it unless you were planning a major expansion, or you just couldn't get it to work once again.