Hi, I hope someone can help me with this one. I have fitted a Danfoss controls pack to my existing Potterton Prima C boiler. It only had a basic timed on /off before. Everything works as it should except that the boiler does not switch off when the central heating side has been on and is turned off either by room stat or timer. The programmer says it is off, with no lights on, but the boiler keeps firing up until the direct power to it is turned off. I am getting advice from Danfoss who seem to think that the boiler is being kept live by back voltage from the three way valve (some 50-100 volts). The boiler has pump over run and the system is fully pumped. Potterton refuse to tell me if the boiler(it's quite old) is compatible with a sprung 3port valve. I can't afford to get someone in and don't know where to go from here. Help please.