these boilers are prone to lock out first the flame sensing probes should be checked and cleaned then the leads of these probes should be inspected. if the probes and leads are ok look at the circuit board as you look at it on the right hand side towards the back they have scorch marks on where the gas valve joins the circuit board if you have black on the pcb then you will need a new pcb and gas valve also the boiler stat and over heat stat play up on these boilers are your rads hotter than normal ?
also in the fan unit you have a venturi if this is blocked then the boiler will lock out so this will need to be removed and cleaned out.
start with the spark electrodes and leads
then the venturi then the stats then pcb and gas valve
optigas
November 2009
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