I have a problem with my CSI 120 T boiler, the fan runs constantly when switched on even with the timer in the off position.When swithed to auto or on position the boiler fires up and heats the rads for about a minutes then the burner knocks off (fan still running), about 5 minutes later it starts to heat the water again, however the DHW seems to be working okay. Anyone have any ideas ?

roger f, February 2012