When your Worcester Bosch boiler displays a fault code, it’s doing you a favour by signalling exactly what’s wrong in a language only trained professionals (or handy guides like this one) can decode. Whether it’s a burner control issue, a safety temperature limiter fault, or a problem with water pressure, these codes give you a crucial heads-up before a minor issue becomes a significant breakdown.
This guide explains the most common Worcester Bosch boiler error codes found in UK homes, what they mean, and what actions to take, from resetting the boiler to calling a Gas Safe engineer. With error codes ranging from EA 227 to F0 238, we’ll help you understand what’s flashing on your boiler display.
This blog breaks down the most common boiler fault codes, what they mean, and when to call a gas-safe engineer to keep your heating running safely.
Experiencing boiler trouble in your home? At Happy Dog Plumbing & Heating, we’re here to help with fast diagnostics, honest advice, and expert repairs. Call us on 0208 8797372 or email hello@happydogplumbing.london because no one should be left in the cold.
Understanding Worcester Bosch boiler error codes doesn't have to be a headache. At Happy Dog Plumbing and Heating, we are well aware of the codes and fix the faults quickly, safely, and with a smile.
Understanding Worcester Bosch Boiler Error Codes
Modern Worcester Bosch boilers are engineered for efficiency and reliability, but like any system, they can encounter problems. When a fault arises, your boiler typically displays a code to help identify the issue. Knowing what these error codes mean can help you take the right action, whether it’s something simple you can fix yourself or a sign that you need to call a qualified gas-safe engineer.
Let’s explore the most common Worcester Bosch error codes found in the UK homes.
1. EA 227, EA 229 – No Flame Detected Or Flame Signal Loss
These burner control faults mean the boiler has failed to detect a flame or has lost the signal during operation. This could result from gas supply, ignition electrode, or flue gas issues. Check your gas meter and ensure there’s no disruption. If the issue persists, reset the boiler using the reset button or contact a gas-safe engineer.
2. E119 & E1017 – Low Water Pressure
These codes typically indicate that system pressure has dropped below safe operating levels. You can resolve this by topping up your boiler using the external filling loop. Most boilers require around 1.5 bar. If the pressure keeps dropping, there may be a leak or an issue with the pressure sensor.
3. C6 215 – Fan Speed Too High Or Too Low
This error relates to the fan inside the boiler that helps expel flue gases. Variations in fan speed could be due to a blockage, a faulty fan, or a wiring issue. As fan control is critical to combustion, always call a qualified technician to handle this fault.
4. E9 – Overheating Or Safety Temperature Limiter Tripped
This critical fault occurs when the safety temperature limiter detects overheating. Causes include a faulty pump, a blocked heat exchanger, or sludge in the system. Turn off the boiler and do not attempt to restart until it’s been inspected.
5. A1 – Pump Stuck, Running Dry, Or Air In System
This fault indicates your boiler’s pump is either jammed, not circulating water properly, or running without sufficient water. Bleeding the radiators or repressurising the system may help. Persistent A1 faults often point to pump replacement needs.
6. F7 – False Flame Detection (Flame When Off)
This fault is linked to the boiler incorrectly detecting a flame when it’s not supposed to. Possible culprits include wiring, ignition electrode, or burner control issues. Reset the boiler first. If the issue returns, call an engineer.
7. FD – Power Interruption Or Accidental Reset
The FD code usually appears after a power cut or manual reset. It’s not a fault but a notification. Simply press the spanner return button and allow the boiler to run normally.
8. C1 – Fan Stopping During Operation
This suggests the fan has unexpectedly stopped while the boiler is in use. Fan failure, electrical faults, or flue gas problems could cause it. Since fan operation is essential for boiler safety, call an expert.
9. H09 – Maintenance Required (Pump/PCB Communication)
This code indicates that routine maintenance is due or there’s a communication error between the pump and the printed circuit board (PCB). This is often not an urgent fault. It should be checked during your annual boiler service.
10. SE – Service Reminder (Not A Fault)
The SE code simply reminds you that a service is due. Keeping up with boiler servicing helps prevent future faults and maintains your warranty.
11. 1021 – Defective Hot Water Temperature Sensor
This fault points to an issue with the hot water temperature sensor. A wiring fault or sensor failure could affect your hot water supply. You’ll need a gas-safe engineer to inspect it.
12. F0 238 – Gas Valve or Control Box Error
This critical error suggests a fault with the gas valve or control unit that regulates gas flow. It can cause burner control issues or a complete lockout. Call a qualified engineer to investigate safely.
Contact HappyDog Plumbing & Heating
Preventing Common Boiler Faults With Happy Dog Plumbing & Heating
At Happy Dog Plumbing and Heating, we’ve helped hundreds of South London homeowners get their Worcester Bosch boilers back up and running quickly, safely, and with zero stress. From F20 faults to pressure drops and sensor issues, we know these error codes and fix them precisely.
With over 50 years of combined experience, our Gas Safe registered engineers bring expert care to every callout, whether a quick reset or a more complex burner control repair. We take pride in honest advice, transparent pricing, and showing up exactly when we say we will.
If your Worcester boiler is flashing an error code or behaving strangely, don’t ignore it. Call Happy Dog Plumbing and Heating on 0208 8797372 or email hello@happydogplumbing.london, and let’s get your home warm and safe again in no time.
Frequently Asked Questions
1. What is the most common boiler fault?
Low water pressure is the most common fault, usually fixed by repressurising the boiler using the external filling loop.
2. What are the fault codes on a Vaillant boiler?
Vaillant boiler fault codes help identify issues like ignition failure, sensor errors, low pressure, and communication faults with components.
3. What are boiler fault codes for combi boilers?
Combi boiler fault codes highlight problems such as low pressure, ignition failure, temperature sensor faults, or blocked condensate pipes.
4. What is the PCB fault code on a Vaillant boiler?
F61 or F62 valiant boiler fault codes typically indicate a problem with the PCB or gas valve operation.
