hi,f4 fault code is a failure to ignite code.the boiler tries to ignite,(sequance of operation)and failes, the pcb then shuts the boiler down untill the user resets it,it can happen sometimes.with regard to the blue tap,there is a lcd disply on the boiler wich acts as a temprature and ch pressure gauge this should be set at1.1bar.to top the pressure up just turn the tap slowly anti clockwise then close when correct pressure reached.hope this helps
grant
February 2008
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