hi there my baxi combi 105e iam not getting any hot water from taps. only way i can get hot water is by switching on the central heating .on the panel there should be 4 green lights the 2nd light along does not light up.picture of a top above it that space has no light on at all there is no red light flashing to say there is a fault would a service fix it or is this going to be a costly repair thanks for any help