Worcester Bosch 2924 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch 2924 fault code mean?
Fault code 2924 is a locking error that causes the boiler to shut down completely and refuse to restart without a manual reset. It signals a problem detected within the appliance electronics — meaning the PCB (printed circuit board) is either faulty itself or is failing to receive the signal it expects from another component. On the Greenstar 8000 in particular, a well-documented additional cause is failed gas valve coils: when the coils stop working correctly, the PCB receives no valid reading from the valve and logs this code. Codes 2923, 2924, 2925, and 2926 all sit in the same appliance electronics fault family — 2923 and 2924 point most directly to electronics failure or a missing valve signal, while 2925 and 2926 also implicate the gas valve and its associated components. If a single reset clears the fault and it does not return, no further action may be needed; if the lockout recurs, a Gas Safe engineer will need to investigate and likely replace either the gas valve or the PCB.
General guidance only — not a substitute for professional advice. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Failed gas valve coils (Greenstar 8000 and CDi models) Common
On the Greenstar 8000 and older CDi-series boilers, the coils within the gas valve can fail electrically. When this happens the PCB receives no valid response from the valve and raises a 2924 lockout. An engineer will check the coils for continuity and confirm whether voltage is reaching the valve before deciding whether to repair or replace it.
- Stuck or damaged bearing plate membrane Sometimes
The Greenstar 8000 and certain CDi models have a non-return diaphragm (sometimes called a bearing plate membrane) located above the fan. As these boilers age this membrane can become stuck or deteriorate, restricting gas flow through the valve assembly. The boiler's electronics interpret the resulting abnormal readings as an appliance fault and trigger a 2924 lockout. Worcester Bosch's own documentation lists a damaged or stuck diaphragm as one of the recognised causes for this fault family.
- Faulty PCB (appliance electronics) Sometimes
If the PCB itself is failing — due to age, component degradation, or electrical damage — it may generate spurious fault codes including 2924 even when all other components are working correctly. Signs that the PCB rather than the valve is the root cause include random or repeated lockouts across different fault codes, erratic fan or pump behaviour, and the fault returning immediately after a gas valve replacement.
- Faulty sensor providing incorrect data to the PCB Rare
In some cases neither the valve nor the PCB is the primary culprit. A defective sensor (such as a temperature or flow sensor) can feed the PCB inaccurate readings that trigger a protective lockout and display this fault code. An engineer will rule this out during diagnostics before committing to a more expensive component replacement.
How to fix it
- Reset the boiler once or twice DIY safe
Press and hold the reset button (or follow the reset procedure in your boiler's user guide) for the model you own. Wait a few minutes for the boiler to attempt a restart. If it lights successfully and stays running, monitor it over the next day or two. Worcester Bosch's own guidance for codes 2923 and 2924 states that a reset should be tried first — if the fault clears and does not return, no further action is necessary.
- Check your gas supply is working DIY safe
Before calling an engineer, confirm that other gas appliances in your home (such as a hob or gas fire) are working normally. If they are not, contact your gas supplier rather than a boiler engineer, as the fault may lie with the incoming supply rather than the boiler.
- Note whether the fault returns and how quickly DIY safe
Keep a brief note of how often the lockout occurs and whether it happens at a particular time of day or under a specific demand (e.g. only on heating, only on hot water). This information is genuinely useful to the engineer and can speed up diagnosis.
- Call a Gas Safe registered engineer to diagnose the fault Gas Safe engineer
Because fault 2924 points to either the gas valve or the PCB — both of which are internal components — all further investigation must be carried out by a qualified Gas Safe registered engineer. Do not remove the boiler casing or attempt to inspect internal parts yourself. Doing so is unsafe and will invalidate your warranty.
- Engineer to test the gas valve coils and check for voltage Gas Safe engineer
The engineer will use a multimeter to check for continuity across the gas valve coils and confirm that the correct voltage is reaching them. They will also inspect the valve's inlet filter for any blockage. On Greenstar 8000 and CDi models they should also inspect the bearing plate membrane for signs of sticking or damage, as this is a known issue on aged examples of these boilers.
- Engineer to replace the gas valve if coils or diaphragm have failed Gas Safe engineer
If the coils show no continuity, voltage is absent, or the membrane is damaged, the gas valve assembly will need to be replaced. This is a Gas Safe-controlled task involving the gas pipework and must not be attempted by an unqualified person.
- Engineer to replace the PCB if the gas valve is confirmed to be in good order Gas Safe engineer
If the gas valve and its associated components test correctly but the 2924 fault persists, the PCB itself is the likely culprit and will need to be replaced. Given the cost of PCB replacement relative to the value of an older boiler, the engineer may also advise whether a new boiler represents better value — particularly if the appliance is over ten years old.
Parts you may need
- Gas valve assembly (Greenstar 8000 / CDi) · from £120
- Bearing plate membrane / diaphragm · from £35
- PCB (appliance electronics board) · from £200
- Gas valve coil set · from £45
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £180–£450, depending on the underlying cause.
Frequently asked questions
Can I fix Worcester Bosch fault code 2924 myself?
The only safe DIY steps are resetting the boiler (up to two or three times) and confirming your wider gas supply is working. Every other aspect of diagnosing and repairing this fault — testing the gas valve, inspecting internal components, replacing the PCB — must be carried out by a Gas Safe registered engineer. Opening the boiler casing yourself is both dangerous and likely to void your warranty.
What is the difference between fault codes 2923, 2924, 2925, and 2926?
All four codes sit within the same appliance electronics fault family on Worcester Bosch boilers. Codes 2923 and 2924 most directly indicate a fault with the appliance electronics (PCB) or a missing signal from the gas valve, and Worcester Bosch's guidance for both is to reset first and replace the electronics if the fault persists. Codes 2925 and 2926 additionally implicate the gas valve itself, so an engineer will check and potentially replace the valve as well as the PCB when those codes appear. In practice, the diagnostic process for all four is very similar.
How much does it cost to fix fault code 2924 on a Worcester Bosch boiler?
For most households the repair cost falls between £180 and £450 depending on which component is at fault and where in the UK you are. A gas valve replacement typically costs £180–£300 all in, while a PCB replacement usually runs £300–£450. Engineers in London and the South East tend to charge more than those in other regions. If your boiler is also out of warranty and over ten to twelve years old, it is worth asking your engineer whether repair or full replacement makes more financial sense — a new PCB on an ageing boiler can cost more than the boiler's remaining useful value.
Why does fault code 2924 keep coming back after a reset?
A fault that clears on reset but returns within hours or days almost always indicates a genuine component problem rather than a one-off glitch. On the Greenstar 8000 the most likely culprit is failing gas valve coils or a stuck bearing plate membrane; on the Greenstar 2000 and other models the PCB itself is more often responsible. Repeated lockouts should not be ignored — each time the boiler shuts down without heating or hot water, and continuing to reset without a proper diagnosis risks masking a safety-related fault.