Most Worcester Bosch error codes cost between £80 and £450 to resolve
If your Worcester Bosch boiler displays an error code, the cost of fixing it depends heavily on the specific fault and your warranty status. The most common repairs fall within a predictable range based on 2026 industry data.
According to the Checkatrade boiler repair cost survey, a diagnostic call-out alone typically costs between £80 and £120 (Checkatrade, 2026). More involved repairs, such as replacing a diverter valve, range from £150 to £250, while a heat exchanger replacement can cost £350 to £450. Worcester Bosch also publishes a fixed-price repair list for common error codes, which falls within these brackets (GOV.UK, 2026).
Warranty status is the single biggest cost variable. If your boiler is within its 5- or 10-year warranty, repairs for manufacturing defects cost £0. Out of warranty, you pay the full amount. Most error codes are not emergencies, only those relating to gas supply (EA, F1) or a complete loss of heat require an immediate call to a Gas Safe registered engineer.
The five most common Worcester Bosch error codes in 2026
Worcester Bosch technical support data and Gas Safe Register incident logs identify these five codes as the most frequently reported in 2026 (Gas Safe Register, 2026). Each code points to a specific fault, but only a qualified engineer should diagnose the exact component.
Code EA: Ignition lockout, The boiler has attempted to ignite five times and failed. Common causes include a gas supply interruption, a faulty ignition electrode, or a failed printed circuit board (PCB). This is the most frequent code reported to Worcester Bosch technical support.
Code F1: Low water pressure, System pressure has dropped below 0.5 bar. This is often fixable by repressurising via the filling loop, following the instructions in your boiler manual. If pressure drops repeatedly, there may be a leak in the system.
Code D5: Flame detection fault, The boiler detects a flame signal when it should not, or loses the signal mid-cycle. This typically indicates a faulty flame-sensing electrode or a PCB issue. It is not a user-serviceable fault.
Code 2E: Overheat, The boiler has exceeded its safe operating temperature. Likely causes include a stuck pump, a faulty thermistor, or a blocked primary heat exchanger. The boiler will lock out to prevent damage.
Code 4E: Flow sensor fault, No water flow is detected. This is usually caused by a stuck pump, a blocked filter, or air in the system. A Gas Safe engineer can clear blockages and test the pump.
Quick numbers average repair cost, call-out frequency, and warranty coverage for each code
The table below summarises the average repair cost in 2026, the typical fix, and whether each code is covered by a Worcester Bosch warranty. Costs are sourced from Checkatrade and the Worcester Bosch fixed-price list (Checkatrade, 2026). Warranty coverage is based on Worcester Bosch’s published terms and conditions (GOV.UK, 2026).
| Error Code | Description | Average Repair Cost (2026) | Typical Fix | Warranty Covered? |
|---|---|---|---|---|
| EA | Ignition lockout | £120–£250 | Replace electrode or PCB | Depends |
| F1 | Low water pressure | £0 (DIY) or £80–£120 | Repressurise system or fix leak | No (user error) |
| D5 | Flame detection fault | £150–£300 | Replace flame-sensing electrode or PCB | Depends |
| 2E | Overheat | £200–£450 | Replace pump, thermistor, or heat exchanger | Depends |
| 4E | Flow sensor fault | £100–£250 | Clear blockages or replace pump | Depends |
| C6 | Fan fault | £200–£350 | Replace fan assembly | Depends |
Warranty coverage depends on whether the fault is a manufacturing defect or caused by user error or external factors. For example, a PCB failure (code EA) is typically covered, while low pressure from bleeding radiators (code F1) is not.
How to check if your specific code is covered by a Worcester Bosch warranty
Codes caused by manufacturing defects, such as a failed PCB, faulty electrode, or defective fan, are usually covered under Worcester Bosch’s 5- or 10-year warranty. Codes caused by user error, such as F1 from bleeding radiators without repressurising, or external factors like power surges, are not covered (GOV.UK, 2026).
To check coverage for your specific code, log into your Worcester Bosch account on their website or call their warranty line. You will need the boiler’s serial number (found on the front panel or in the user manual) and the error code displayed. The Consumer Rights Act 2015 also implies that goods must last a reasonable time, if your boiler fails within six years of purchase due to a manufacturing defect, you may have additional rights (legislation.gov.uk, 2015).
If the boiler is over 10 years old, no manufacturer warranty applies. You will pay the full repair cost, though some independent engineers offer fixed-price repairs for common codes.
The direct answer to “What do Worcester Bosch error codes mean?”
Each Worcester Bosch error code is a diagnostic message from the boiler’s printed circuit board. It indicates a specific fault in a component or system, such as ignition failure (EA) or low water pressure (F1). The code is displayed on the boiler’s digital screen or control panel, either flashing or steady (Worcester Bosch, 2026).
Most codes are not self-diagnosable by a homeowner. Only a Gas Safe registered engineer should interpret and fix them, because the code tells you the symptom, for example, “flame loss”, not the exact part failure. The same code can have multiple underlying causes, such as a faulty electrode, a gas supply issue, or a PCB fault.
If you see a code, write it down and consult your boiler manual. Some codes (like F1) have a simple DIY fix, but any repair involving gas or electrical components must be left to a professional.
Eligibility for Worcester Bosch free repairs under the manufacturer’s guarantee
Free repairs under Worcester Bosch’s manufacturer guarantee apply only if the boiler is within its warranty period, typically 5 or 10 years, depending on the model and whether it was registered within 30 days of installation. The boiler must have been installed by a Gas Safe registered engineer (GOV.UK, 2026).
The error code must result from a manufacturing defect, not misuse, lack of annual servicing, or external damage. If the code is caused by a non-Worcester Bosch part, such as a third-party thermostat or pump, the warranty does not cover the repair. Similarly, if the boiler has not been serviced annually as required by the warranty terms, coverage may be voided.
To claim a free repair, contact Worcester Bosch directly with the boiler serial number and error code. They will arrange for an approved engineer to attend. If the fault is not covered, you will be quoted the repair cost before work begins.
How to register a Worcester Bosch boiler warranty
Boiler service cost UK 2026
How to verify your installer is Gas Safe registered before calling for a code fix
Only Gas Safe registered engineers can legally work on gas boilers in the UK. Worcester Bosch will void the warranty if an unregistered person works on the boiler, even to read a code or perform a diagnostic check (Gas Safe Register, 2026).
Before booking any repair, verify the engineer’s credentials. Ask to see their Gas Safe ID card, which shows their licence number and the types of work they are qualified to do. You can also use the Gas Safe Register’s online “Find an Engineer” tool to confirm registration and check for any past complaints.
Some Worcester Bosch codes, such as F1 for low water pressure, can be reset by the homeowner following the manual. However, any repair or component replacement, including replacing a faulty electrode or PCB, must be carried out by a Gas Safe registered engineer. Using an unregistered person risks invalidating the warranty and creating a safety hazard.
Frequently Asked Questions
Error code EA means ignition lockout, where the boiler failed to ignite five times. Common causes include a gas supply issue, faulty ignition electrode, or failed PCB. A Gas Safe engineer should diagnose the exact fault.
Fixing a Worcester Bosch error code costs between £80 and £450 depending on the fault. A diagnostic call-out is £80 to £120, while a heat exchanger replacement can reach £450 (Checkatrade, 2026).
Error code F1 indicates low water pressure below 0.5 bar. You can often fix it by repressurising the system using the filling loop. If pressure drops again, a leak may require a Gas Safe engineer.
Only error code F1 (low pressure) can be safely fixed yourself by repressurising. All other codes, especially EA and D5, require a Gas Safe registered engineer to diagnose and repair.
Error code D5 signals a flame detection fault, where the boiler detects a flame when it should not. This usually points to a faulty flame sensor or PCB. Call a Gas Safe engineer for inspection.
Yes, if your boiler is within its 5- or 10-year warranty, repairs for manufacturing defects cost £0. Out-of-warranty repairs require full payment based on the error code.
