Chaffoteaux maury britony combi 100 se, fault keeps changing!?

Hi
I'm hoping someone an help. My boiler failed on tues, showing a fault 40 60 80. It was my fault as I had ignored an intermittent problem where I would demand hot water and it would trip out and need re-setting ( didn't happen every time). Anyway called plumber and told him fault he came and changed the aps, this didn't fix so he tested the feed from the fan to aps which was positive then tested feed from pcb to fan which was neg on this basis he ordered a pcb, he has been today to fit and now the fault has changed to 70 80. Plumber thinks he has wrong pcb, could this be correct or could the problem not be related to pcb. Help I'm sick of cold showers!