code 03 is flashing which reading the owners manual is a flu problem it is a synergy e

eddie coates, May 2011

flue venturi fault [blocked]
could just replace [or clean] the venturi
personally id the replace the fan as well, just to be on safe side
if the venturi has gotten to the stage of being blocked
chances are the fan performance has deteriorated as well
well known fault on vokera boilers

manwithnoname, May 2011