Worcester Bosch F0 272 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch F0 272 fault code mean?
The F0 272 code appears on Worcester Bosch Greenstar i combi boilers and indicates a problem with the Burner Control Unit (KIM) — the dedicated electronic module that manages burner operation and ignition sequencing. When this code is active, the boiler's red fault LED will flash and the appliance will lock out. The F0 prefix is a general internal electronics fault category on Worcester Bosch boilers; the sub-code 272 specifically points to the KIM's wiring or the unit itself. Other F0 sub-codes you may encounter on the same platform include F0 224 (PCB internal fault), F0 248 (Heat Control Module communication error), and F0 256 (general control electronics mismatch) — all share the same red-flashing-LED presentation and similarly require a Gas Safe engineer to resolve.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. 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
- Burner Control Unit (KIM) wiring fault Common
The wiring harness connecting the KIM to the main PCB can develop loose terminals, corrosion, or chafing over time. Even a marginal connection can cause the KIM to report a failure and trigger F0 272. This is the most direct cause named in Worcester Bosch's own service documentation for this sub-code.
- Faulty or failed Burner Control Unit (KIM) Common
The KIM module itself can fail internally — capacitor degradation, moisture ingress, or simple age-related component failure. When the unit stops responding correctly to the PCB's commands, F0 272 is logged and the boiler locks out.
- Heat Control Module (HCM) not seated correctly or faulty Sometimes
The HCM works alongside the KIM and PCB to coordinate boiler operation. If it was improperly installed during a previous service, knocked loose, or has developed an internal fault, it can disrupt communication across the control system and produce an F0 272 reading.
- PCB fault or damage Sometimes
The main Printed Circuit Board orchestrates all electronic communication in the boiler. A damaged PCB can send incorrect signals to the KIM or misinterpret responses, causing the control system to log an F0 fault. Worcester Bosch service notes flag PCB damage as a possible root cause when the fault LED flashes alongside an F0 code.
- General wiring or connector degradation Sometimes
Broader wiring issues — oxidised plugs, damaged cable insulation, or connectors that have worked loose due to vibration — can mimic a KIM fault by interrupting the signal path between components. These are worth checking before replacing expensive modules.
How to fix it
- Reset the boiler once DIY safe
Press and hold the reset button (usually marked with a flame symbol) for approximately 3 seconds. Allow the boiler to complete its start-up sequence. If the F0 272 code clears and the boiler runs normally, monitor it closely. If the code returns within a short time, do not keep resetting — repeated resets will not fix an underlying electronics fault and can mask important diagnostic information for the engineer.
- Check the gas supply to the property DIY safe
Confirm that other gas appliances (hob, gas fire) are working normally and that your gas meter has not been isolated or run out of credit on a prepayment meter. If there is no gas supply to the property, contact your gas supplier before calling a boiler engineer.
- Note down the exact code displayed and any recent history DIY safe
Take a photograph of the fault code on the display and make a note of when the fault first appeared, whether it followed a power cut or recent service, and how many times you have reset the boiler. This information helps the engineer diagnose the fault faster and can reduce your callout time.
- Do not open the boiler casing or attempt internal checks Gas Safe engineer
The KIM, HCM, PCB, and all associated wiring are located inside the boiler casing. Accessing them involves working near live electrical components and gas-related parts. This work must only be carried out by a Gas Safe registered engineer with the appropriate diagnostic tools and Worcester Bosch technical knowledge.
- Have a Gas Safe registered engineer inspect and repair the boiler Gas Safe engineer
A qualified engineer — ideally one who is Worcester Bosch accredited — will use manufacturer diagnostic tools to confirm whether the fault lies with the KIM wiring, the KIM unit itself, the HCM, or the PCB. They will reseat or replace the affected component, test all related connections, and verify correct boiler operation before leaving. Ask to see their Gas Safe ID card before any work begins.
Parts you may need
- Burner Control Unit (KIM) · from £180
- Heat Control Module (HCM) · from £120
- Main PCB (Printed Circuit Board) · from £280
- Wiring harness / connector loom · 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 £150–£450, depending on the underlying cause.
Frequently asked questions
Can I fix Worcester Bosch F0 272 myself?
No. While a single reset is safe to try, F0 272 points to a fault inside the boiler's control electronics — the KIM, HCM, or PCB. Working on these components requires dismantling the boiler casing, handling live electrical parts, and working near gas components, all of which are legally restricted to Gas Safe registered engineers. Attempting DIY repairs will also void your boiler warranty.
How much will it cost to repair F0 272 in the UK?
Most homeowners pay between £150 and £450 including parts, labour, and VAT. A wiring or connector fix sits at the lower end of that range (roughly £100–£200), while replacing the KIM typically costs £200–£350. If the PCB turns out to be the root cause, costs can rise to £450–£700 — that scenario is less common but worth knowing about if your boiler is older and the engineer finds wider electronic damage.
What is the difference between F0 272 and other F0 codes like F0 224 or F0 248?
All F0 codes on Worcester Bosch boilers indicate an internal electronics fault, and they share the same red-flashing-LED lockout presentation. The sub-code tells the engineer which specific part of the control system has flagged a problem: F0 272 points to the Burner Control Unit (KIM) and its wiring, F0 224 relates to an internal PCB fault, and F0 248 typically indicates a communication issue with the Heat Control Module. Your engineer will use the full code — both the F0 prefix and the three-digit number — to direct their diagnosis.
My boiler keeps coming back with F0 272 after being reset — should I replace it?
A recurring F0 272 fault that returns shortly after every reset usually means a component has genuinely failed rather than experienced a one-off glitch. Have an engineer carry out a proper diagnosis before deciding. If your Greenstar i combi is over 10 years old and the repair quote is high relative to the boiler's value, replacing it with a modern A-rated model may be more cost-effective in the long run. A reputable engineer should give you an honest assessment of whether repair or replacement makes more financial sense.