Worcester Bosch 2967 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch 2967 fault code mean?
Fault code 2967 appears on Worcester Bosch Greenstar 8000 series boilers and signals that the control board has detected an excessively large temperature gap between the flow temperature sensor and the heat exchanger safety limiter. In straightforward terms, heat is accumulating inside the heat exchanger much faster than the system can safely carry it away, so the boiler shuts itself down as a precaution. The Greenstar 8000 range uses four-digit numeric codes rather than the alphanumeric codes (such as E9) found on older Worcester Bosch models — 2967 is specific to this differential temperature fault. A variant labelled 2967 B indicates the same underlying issue. Because the boiler cuts out to prevent damage, this is a locking fault: it will display a flashing code alongside a warning triangle and will not restart without a manual reset. Do not repeatedly reset without addressing the root cause, as this can make matters worse.
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
- Sludge or limescale blocking the heat exchanger Common
Over time, magnetite sludge and — particularly in hard-water areas — limescale accumulate inside the heat exchanger. This restricts water flow, causing heat to build up rapidly and triggering the safety limiter. It is the most frequently identified root cause of this fault on the Greenstar 8000.
- Circulation pump failure or poor pump performance Common
The pump is responsible for constantly moving heated water around the system. If it seizes, develops an airlock, or simply loses efficiency, hot water stagnates in the heat exchanger and temperatures spike until the safety cut-out activates.
- Faulty or incorrectly connected temperature sensor Sometimes
If the flow temperature sensor or the heat exchanger limiter sensor is sending inaccurate readings — due to a failed sensor, a loose connector, or incorrect wiring — the control board may see a false differential and lock the boiler out even when actual temperatures are normal.
- Air trapped in the system Sometimes
Air pockets restrict circulation in much the same way as sludge. If the automatic air vent is not functioning properly, or radiators have not been bled, airlock-related circulation loss can cause localised overheating at the heat exchanger.
- Restricted flow from isolation valves or a sticky diverter valve Sometimes
Debris can lodge in isolation valves or cause a diverter valve to sit in a partially closed position, reducing water flow through the heat exchanger and creating the temperature differential that triggers this code.
How to fix it
- Reset the boiler once DIY safe
Locate the mode selector on the front panel and turn it fully anticlockwise to the reset position (indicated by a flame symbol with a line through it). Hold for approximately two seconds, then return it to your normal heating or auto setting. The boiler will attempt to restart. If it locks out again immediately, do not keep resetting — move on to the checks below.
- Check your system pressure DIY safe
Look at the pressure gauge on the boiler. When the system is cold it should read between 1.0 and 1.5 bar. If it is below 1 bar, top it up using the filling loop until it reaches around 1.2 bar, then attempt another reset. If pressure is already correct, this is not the cause.
- Bleed your radiators DIY safe
Starting with the radiator furthest from the boiler, use a radiator key to open the bleed valve until water (not air) comes out, then close it. Work your way back towards the boiler. Afterwards, recheck system pressure and top up if it has dropped below 1 bar. This addresses trapped air that can impair circulation.
- Check that your gas supply is working DIY safe
Confirm that other gas appliances in your home (hob, gas fire) are working normally and that your gas meter isolation valve is fully open. If you have no gas supply, contact your gas supplier rather than a boiler engineer.
- Contact a Gas Safe registered engineer to investigate circulation and heat exchanger Gas Safe engineer
If the boiler continues to lock out after your basic checks, an engineer should inspect the system. They will typically isolate and drain the boiler, check for blockages at the heat exchanger and isolation valves, flush the boiler circuit, and assess whether a full power flush of the system is needed to clear sludge or scale.
- Engineer to test both temperature sensors Gas Safe engineer
Using a multimeter, the engineer should verify that the flow temperature sensor and the heat exchanger safety limiter are reading correctly and that all wiring connections are secure and correctly seated. A faulty or poorly connected sensor can generate a false fault code.
- Engineer to inspect and test the circulation pump Gas Safe engineer
The engineer will check pump speed, look for signs of seizure or airlocking, and confirm adequate water flow through the heat exchanger. A pump that is running but underperforming may need servicing or replacement.
- Engineer to carry out a power flush if sludge or scale is found Gas Safe engineer
Where significant magnetite sludge or limescale is identified, a full power flush of the central heating system will be required to restore proper flow. The engineer may also recommend fitting a magnetic filter to prevent recurrence.
- Engineer to replace faulty components as required Gas Safe engineer
Depending on findings, the engineer may need to replace the flow temperature sensor, the heat exchanger limiter sensor, the circulation pump, or — in more severe cases — the heat exchanger itself. Only Gas Safe registered engineers should carry out these replacements on a gas appliance.
Parts you may need
- Flow temperature sensor (NTC sensor) · from £25
- Heat exchanger safety limiter / high-limit thermostat · from £35
- Central heating circulation pump · from £85
- Magnetic system filter (e.g. Fernox TF1, Magnaclean) · from £55
- Heat exchanger (primary) · from £280
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 £150–£450, depending on the underlying cause.
Frequently asked questions
Can I keep resetting fault code 2967 until an engineer arrives?
You can try a single reset to see if the boiler recovers, but you should not keep resetting it repeatedly. Code 2967 is a locking fault triggered by a genuine safety condition — heat building up inside the heat exchanger beyond acceptable limits. Forcing restarts without fixing the underlying problem risks damaging the heat exchanger or other components, potentially turning a relatively affordable repair into a much more expensive one.
How much does it typically cost to fix Worcester Bosch fault code 2967 in the UK?
For the most common causes — a sensor replacement or a power flush to clear sludge — most homeowners pay somewhere between £150 and £450 including labour. A straightforward sensor test and replacement is usually at the lower end, while a power flush of a heavily contaminated system sits towards the higher end of that range. If the engineer finds that the heat exchanger itself needs replacing, expect costs of around £400–£650 once parts and labour are included. A new PCB, if required, is typically the most expensive single repair at £430–£780, though this is a less common outcome for this particular fault.
Is fault code 2967 the same as an E9 fault on older Worcester Bosch boilers?
They are related but not identical. The Greenstar 8000 series uses four-digit numeric codes rather than the alphanumeric codes found on earlier Worcester Bosch models. E9 on older models broadly indicated overheating or a heat exchanger temperature issue, and 2967 covers similar territory — a temperature differential fault at the heat exchanger. However, the exact diagnostic logic differs between the two boiler generations, so an engineer familiar with the Greenstar 8000 platform should always be consulted for this code.
Will a power flush definitely fix a 2967 fault?
A power flush is the right fix when sludge or limescale build-up is causing restricted flow through the heat exchanger — and that is indeed the most common root cause. However, if the fault is actually down to a failing circulation pump, a faulty sensor, or a wiring issue, a power flush alone will not resolve it. A Gas Safe engineer should diagnose the actual cause first before deciding on the appropriate repair, rather than going straight to a power flush without checking sensors and pump performance.