Can someone help please. I have a saunier duval 30e with a problem. The radiators are hot but when i turn on the tap the boiler fails to kick in. I have replaced the DHW micro switch but still not working.However,if i remove the diverter switch and push and hold the pin in the diverter valve in manually the boiler fires up and the water goes hot. I dont know what part to replace.Is it the diverter switch or a diaphragm as its not getting a sign that demand is needed?Hope someone can help and thanks for reading. 