Worcester Bosch Fault Codes — Complete UK Reference
Worcester Bosch Greenstar and Lifestyle boilers show fault codes on the front display. Most fall into six families — ignition, pressure, sensor, fan, PCB and gas. Here is the definitive list, ranked by frequency in UK homes.
Step-by-step method
EA — No flame detected (ignition lockout)
The most common Worcester fault. Boiler tried to light three times and failed. Causes: no gas at meter, blocked condensate (in winter), dirty ignition electrode, faulty gas valve. Reset once by holding the reset button 3 seconds. If it returns, call a Gas Safe engineer.
E9 / D5 — Overheat lockout
Flow temperature exceeded safe limits. Usually a blocked heat exchanger, sludge in the primary, or a jammed pump. Requires power flush or magnetic filter service.
A281 — Pump not running
PCB cannot detect pump rotation. Either the pump is seized (common after summer standby) or the PCB pump driver has failed. £120–£280 fix.
C6 / C7 — Fan speed fault
Fan not reaching commanded RPM. Blocked flue, failed fan bearing, or loose fan wiring loom. Never bypass — it is a combustion safety interlock.
F0 / F7 — Internal PCB fault
Main control board fault. Reset once; if persistent the PCB needs replacing (£240–£380 fitted).
H07 — Low system pressure
Same as flashing pressure gauge. Top up to 1.2 bar via the filling loop. If it drops repeatedly, see our combi pressure-loss guide.
Frequently asked questions
How do I reset a Worcester Bosch boiler?+
Hold the reset button (usually marked with a flame or 'reset') for 3–5 seconds until the display clears. Only reset a lockout twice — repeated lockouts indicate a fault that needs an engineer.
Which Worcester fault codes can I fix myself?+
Low pressure (H07) and a one-off EA after a gas meter change. Everything else needs a Gas Safe registered engineer by law.