Hi . does this happen on heating and hot water?
Hi , is the blue light flashing either , slow flash ( normally off flashes on, or slow flash ( normally on flashes off ), or fast flash, ?
Ok , so fast flash on blue , what about the other led ?( lockout reset )?
Ok , just reread your description , if you are having fastv flashing on both red and blue this indicates a control board fault , and this will need replacing
To make sure of getting the correct one you will need the boiler GC number. Usually on a sticker , either on top of the boiler or within the casing
Hi , if satisfied with your answer can you please give a positive rating , thank you