Hi, I have had a plumber and a spark out to look at this and they are both scratching their heads and blaming the other - so any suggestios will be gratefully received! I have an oil fired central heating system with two zones. The first zone CH, when turned on at the Horstmann Channel Plus programmer will fire the boiler and heat all the radiators downstairs and the hot water. When I press HW this heats the hot water and turns all the radiators on upstairs. For a few weeks now when the programmer clicks off and the lights go out but the heating remains on upstairs. Even if I turn the dial on the thermostat down I wont hear a click to let me know the heating is going off - it just doesn't register that I have set the temperature and keeps heating the radiators. The thermostat clicks OK when the programmer lights are on but not when the heating is firing with no light. We tried changing the thermostat - but the issue still arises. Changed the Actuator Danfoss HPA2 and still no joy. This problem only seems to occur upstairs and the downstairs section comes on and off correctly and shuts the boiler down (as long as the upstairs heating isn't on at the same time) Now the spark thinks that this may be the timer as the lights are out but the boiler is still firing? Anyone have any input? I just feel we're throwing good money after bad as it seems like guess work