They went bust, no idea how, but anyhow, I have a Navitron tdc3 solar thermal controler and some years ago I saw someone explain in great detail exactly how the special functions, like speed control, worked. Is anyone here a refugee also and has tucked away in their Dropbox Onedrive or filing cabinet somewhere this explanation? Or can help me out with exactly how it works? The instructions in the manual are not very good and still have not evolved for the latest models(made by Sorel) Ta Steve