these boilers do give niggly problems like this!
On the right hand side behind the front panel there is a microswitch, its surrounded by a transparent plastic case that slips off to get at it. Sometimes the plunger which makes the connection on the microswitch sticks and doesnt fully make contact, you can turn h/w tap on/off & observe what it does. youll see the moving part!! c if thats it, ok
spila Chilli heating, September 2009