Hi i was called out to a ravenheat csi 85t today and have fond a problem which stumped me. The boiler operates fine coming on and off ok but continually cycles. it will come on for 1 second at hi flame then drop to low for a second and cut out completley. this process complestes over about 3 seconds and hapeens continually when in ch mode dhw is not effected. bridged out the room stat and still happening. also the boiler is very loud on ignition, seems like over gassing, but burner pressure and rating ok. when the modulator for the gas valve is disconnected when lit all is well. could this be a fault with the gas walve or pcb ?