While you wait for answers, we may have found some information which could help you.
Click here for Central Heating Diagnosis Hot Water
Worcester 30 Cadillac combi boiler won’t fire up and the EA?
Remove boiler cover?
Siemens RDJ10RF thermostat problem?
Vaillant ecotec 831 plus?
Greenstar 24Ri boiler, fast flashing - can I reset?
Oil fired boiler thermostat?