Did mine some years ago. Fiddled for weeks trying to get the thing to work without spending. The box has a series of little plastic cogs, and one tooth on mine had worn, so it ended up mistiming and not resetting a micro switch. As I recall. I had to buy a whole soap dispenser unit that included controller. Having said that, it was in 2005, cost me 65 and it is still working.
Bob Wiltshire, July 2012
