I have a Worcester 28CDi combi. The CH works fine but the DHW has a problem. When i open a hot tap the red light on the front of the boiler indicating hot water demand illuminates. The red light indicating the flame ignition does not come on immediately, it takes a few seconds then the flame comes on but goes out again after approx. 30 seconds. It stays off for a similar time and the cycle repeats itself. The net result is warm then cold water following the flame ignition cycle. Clearly this is not correct, anyone have any ideas?

Lee Baron, February 2009