Hi everyone please help i have a vokera linear 24 boiler which keeps locking out on code 3 which is according to manual a fan flue prob. Flue seems clear to me and to check fan (not sure if this is good idea) but i took the front cover off so i could see it and fired up the hot water and fan comes on fine although did seem a bit noisy. Here is the strange thing tho the flame stayed on didnt lock out so i kept it on and put front cover back on and within 3 seconds it cuts out then if i take cover back off it fires straight up again. Is this indicating the fans not working properly? When i take cover off is it letting funds escape out there which fan is not removing as it should. Please help we are freezing and thanks in advance