Error F0 239

Safety precautions:

- If you smell gas, stop immediately, leave the property and call the gas emergency number. Do not stay in the house.

- Turn the boiler off using the front panel and isolate the electrical supply at the boiler isolator or consumer unit before removing any covers. Also turn off the gas supply if you will be working inside the boiler enclosure.

- Do not work on gas valves, burner assemblies, or replace PCBs/HCMs unless you are Gas Safe qualified. Do not remove safety devices or bypass interlocks.

- Take photos of connectors before you touch them so you can reseat wiring exactly as found.

Initial basic checks a homeowner can do:

1. Note the exact error code display (F0 239) and any additional flashing cause codes or symbols. Photograph the display to show an engineer.

2. Try a basic reset: press the boiler reset button once (follow the manual instructions) and wait to see if the fault clears and the boiler attempts to run.

3. If reset has no effect, isolate power for 30–60 seconds at the boiler isolator or fuse spur, then restore power and check the display again.

4. Check for any recent work or part fitted to the boiler (HCM/code plug or control board changed recently). If a wrong module was fitted, that can cause this fault.

5. Check the boiler service history. If it hasn’t been serviced in 12 months get this information ready for the engineer.

If you are comfortable and competent with basic electrical isolation and small visual inspections (only after power is isolated):

1. Remove the outer case only after the mains is isolated. Keep the front panel screws and note how the panels fit together.

2. Locate the burner control / identification module area (the small plug-in card or connector near the main PCB). On Worcester units this is usually a small module or coded plug adjacent to the PCB.

3. Visually inspect the plug and wiring for signs of damage, pinching, overheating, corrosion, loose wires, or incorrectly seated connectors. Check ignition leads and visible connectors for secure seating.

4. If connectors look loose or dirty, and you are confident the power is isolated, carefully unplug and re-seat the connector(s). Do not force a connector; check for broken plastic lugs. Reassemble covers, re-energise and test the boiler.

5. If the fault clears after reseating, monitor for recurrence. Intermittent reappearance indicates damaged wiring, a failing connector or a faulty module that needs replacing by an engineer.

6. Do not attempt to swap or replace the HCM/module unless you are a qualified engineer—replacement often requires correct coding and testing on gas safety grounds.

When to call a professional and what to tell them:

- Call a Gas Safe registered engineer if the error does not clear after reset/power-cycle, if you found damaged or pinched wiring, if connectors are corroded, or if the error returns intermittently.

- Tell the engineer the exact boiler model (Worcester Bosch GB162), the error code (F0 239), any other displayed cause codes, what you saw when you inspected connectors, and whether any parts (HCM/code plug) were recently fitted.

- The engineer will check wiring continuity, verify the correct HCM/coding card, test and if necessary replace the burner control unit/HCM or PCB and then run gas-safety and combustion checks.

Important reminders:

- Do not attempt internal gas or PCB repairs if you are not Gas Safe registered. Work beyond basic visual inspection and reseating connectors should be left to a professional.

- Keep records and photos of the fault and any checks you did; this speeds diagnosis. The fault is typically fixed by reseating or replacing the HCM/KIM or repairing damaged cabling, but a qualified engineer must complete the repair and safety testing.