Worcester Bosch 533 Compact Fault codes & diagnostics

SuperLock caused by too frequent thermostat overheat detections during burning

HCM problem

Pump stuck or running in air

Flue gas sensor shorted

Domestic hot water sensor defect

EMS communication error

Internal error - replace control board

Airflow stopped during operation

Airflow present during last 24 hours

Fan running too fast

Fan not running

Outdoor sensor defect

No pressure variation detected after switching pump

Water pressure sensor not connected or short-circuit to supply

Return temperature too high

external cut-off switch activated

Temperature difference between flow and safety sensor exceeding limit

Flow sensor shorted

Return temperature higher than supply temperature (some time after burner start)

Preheat sensor on DHW inlet Short Circuit

Supply sensor exceeded 110°C

Flow temperature exceeded 95°

First Safety timing error

Flue gas temperature rising too fast

CH: flue gas temperature rising but supply temperature not

HW: supply temperature too hot

Supply and/or return temperatures do not change after burner start

Internal error call British Gas national help-line 0800 197 5787

Ionisation current detected before burner-start

Ionisation detected after burner stop

Gas valve EV1 leak test failed

Mains power error - electrical power interruption

No feedback from pump