The Real Worcester Boiler Fault Codes (And Why Half the Guides Online Get Them Wrong) Search "Worcester boiler error codes" and you'll find dozens of guides, and a fair number of them mix Worcester's codes up with Ideal, Baxi or Potterton codes without realising it. If you've seen a code like L2 or E110 mentioned somewhere and it doesn't match what your Worcester Bosch display is actually showing, that's why. Worcester's own fault codes follow a different format entirely, usually a letter followed by a single digit (EA, E9, A1, C6, D1), often paired with a three-digit cause number underneath (like EA 227 or E9 219). We have cross-checked Worcester's genuine fault codes against multiple independent Gas Safe engineer sources to put together the list below, so you're working from what your boiler is telling you, not a code chart for a different brand. If you'd rather skip straight to booking help, our Boiler Repair Service in London covers every code on this page, and the number is at the bottom of the guide.
Why Worcester Boilers Show Fault Codes At All Every Worcester Bosch Greenstar boiler runs continuous safety checks on water pressure, flow temperature, flame presence and fan speed. When a reading falls outside a safe range, the control board does one of two things: • •
Blocks temporarily. The boiler pauses for a short period, often without a permanent code, while it waits for a condition (like temperature) to settle. Locks out. A fault code appears on the display, sometimes with a flashing blue light, and the boiler stays off until it's reset or repaired.
A single reset after a lockout is normal. If the same code reappears straight after resetting, that's the point to stop and get it looked at properly, since continuing to reset a gas-related fault isn't safe and can let a small issue turn into a bigger repair.
Worcester Bosch Error Codes: The Full List Code EA (227)
What It Means
Likely Cause
No flame detected after Failed ignition, often a frozen condensate pipe ignition in cold weather
EA (229)
Loss of flame signal during operation
Blocked condensate trap or wind ingress into the flue
E9 (219)
Safety sensor temperature too high
Heat exchanger overheating, maximum 105°C
E9 (224)
Max temperature thermostat activated
Flue gas thermostat overheat
E9 (220/221)
Safety sensor short or open circuit
Faulty or disconnected max temperature sensor
A1
Pump stuck or running dry
Air in the system, seized pump, or low water flow
C6 (215)
Fan speed too high
Blocked flue or faulty fan
C7 (214)
Fan not running
Fan motor or wiring fault
D1 (240/241)
Return sensor error
Sensor wet, damaged, or disconnected
E2 (222/223)
Flow sensor fault
Sensor shorted, disconnected, or damaged
E5 (218/332)
Flow temperature too high
Primary flow sensor has overheated
F0 (238)
Gas valve or control box Fault with the gas valve or main control unit error
F7 (228)
Flame detected before burner start
False flame signal or wiring fault
FA (306/364)
False flame or gas valve leak
Flame detected after burner stop, or a failed valve leak test
9U / C4
Control box or heat control module fault
Loose or defective control board
A7
Domestic hot water sensor defect
Faulty sensor affecting hot water temperature
CC
Outdoor sensor defect
Faulty external sensor on weather compensation systems
No code, flashing Low system pressure tap symbol
Water loss through a leak, or pressure not topped up after bleeding radiators
Worcester's exact codes can vary slightly between the Greenstar i, CDi, 4000, 8000 Style and Si Compact ranges, so if a code you're seeing isn't listed above, read it and the cause number exactly as displayed and check it with an engineer over the phone before booking anyone out.
How to Read Your Worcester Display Correctly Older Greenstar i and CDi models typically show a simple two-character code (like EA or C6) with a small flashing spanner or triangle icon underneath to signal a lockout. Newer Greenstar 8000 Style and Si Compact models display a fuller message, showing the code alongside the three-digit cause number and, in some cases, a short text description. If your boiler has a smart control like Bosch EasyControl or Wave paired with it, the fault will also usually push through as a notification on the app, which is worth checking before you head to the boiler cupboard, especially if it's tucked away in a loft or airing cupboard.
What You Can Safely Check Yourself A handful of Worcester faults are safe to investigate before calling anyone: •
•
•
Low pressure (tap symbol). If your gauge reads below 1 bar, top it up using the external filling loop as described in your boiler manual. If it drops again within days, that's a leak, not a one-off. EA lockout in cold weather. Check the white plastic condensate pipe outside your property first. A frozen pipe is one of the most common causes of an EA fault in winter, and thawing it gently (never with boiling water) often clears it on reset. One reset only. Worcester boilers allow a reset from the display. If the fault returns immediately, stop resetting and call an engineer rather than repeating it.
Everything else on that table involves gas, electrical components, or sealed system parts, and by law needs a Gas Safe registered engineer to open the casing and repair it. Our Worcester Bosch approved service engineers carry manufacturer parts for these exact faults, so most are fixed on the first visit.
Why London Worcester Boilers Fault More Than Average A few things about London specifically make certain faults show up more often here than elsewhere in the UK:
• •
•
Hard water. Much of London sits on a hard water supply, which accelerates limescale build-up inside the heat exchanger, a known contributor to E9 overheat faults over time. Converted and period properties. Older pipework in Victorian conversions and flats leads to airlocks and pressure drops more frequently, which is why A1 and low-pressure faults are common. Our guide on why boilers keep losing pressure covers this in depth. External condensate routing. Many London installations run the condensate pipe outside the property, which is exactly what triggers EA lockouts in cold snaps. Our post on why boilers tend to break at the start of the heating season explains this pattern in more detail.
If you're not sure whether your fault needs an engineer tonight or can wait until tomorrow, our article on how to tell if a boiler error code is serious will help you make that call.
Worcester Boiler Repair Services in London, From Engineers Who Know the Codes At Rapid Response Plumbing and Heating, our Gas Safe registered engineers work on Worcester Bosch boilers across London every week, with over 30 years of combined experience in the trade. When you call about a fault, tell us the exact code and cause number showing on the display, it lets us arrive knowing what to check rather than diagnosing from zero on your doorstep. Whether it's a recurring EA lockout, a pump stuck on A1, a fan fault, or a boiler that keeps dropping pressure, our Emergency Boiler Repair in London is available 24/7 with a fast response and genuine parts carried on the van. If your Worcester boiler is faulting repeatedly and you're weighing up repair versus replacement, our boiler maintenance service can pick up developing sensor and pressure faults before they cause a full breakdown, and if you're based in Hackney specifically, see our dedicated Worcester boiler repairs in Hackney page. Fault code showing right now? Don't keep pressing reset and hoping it clears. Call 07888078885 for same-day Worcester Boiler Repair Services in London, or use our online booking form to book a visit that suits your schedule.
Frequently Asked Questions Are Worcester boiler error codes the same as other brands? No. Worcester Bosch uses its own code format (letters like EA, E9, A1, C6, paired with a threedigit cause number). Codes like L1, L2 or F28 belong to Ideal, Glow-worm or Vaillant boilers, not Worcester, so it's worth double-checking the code matches your brand before troubleshooting. What does EA mean on a Worcester boiler? EA means the boiler failed to detect a flame after ignition (cause 227) or lost an established
flame during operation (cause 229). In winter, this is very often a frozen external condensate pipe rather than an internal fault. What does E9 mean on a Worcester Bosch boiler? E9 signals an overheat fault, where a safety sensor or thermostat has detected the flow temperature or heat exchanger running hotter than the safe limit. This needs checking by a Gas Safe engineer rather than repeated resets. Why does my Worcester boiler keep losing pressure? Repeated pressure loss usually points to a small leak in the system, a faulty pressure relief valve, or trapped air needing to be bled from the radiators. Topping it up once is fine, but if it keeps dropping, book an inspection. How quickly can I get emergency boiler repair in London? Our engineers operate 24/7 across London and can usually reach you the same day. Call 07888078885 and tell us the exact fault code showing so we can prioritise your visit correctly. How much does Worcester boiler repair cost? It depends entirely on the fault and part needed, so we give a clear price after diagnosing the issue rather than quoting blind over the phone. Call us for a straightforward quotation before any work starts.