not sure on these but faults like that tend to point to a flame recognition problem, the boiler thinks that there is not a flame present so cuts off gas and trys again, usually 3 or 5 attempts then will lock out as a safety precaution.
like i said its a long time since ive worked on one of them so cant remember off top of head but id look for something of a flame rec problem, some have seperate rec sensors some use the earth route,
ste, November 2009
