Error S.26

Safety precautions:

1) If you smell gas, evacuate premises immediately, call the emergency gas number and/or emergency services. Do not attempt any checks. 2) Before opening the boiler or touching any electrical parts, isolate the boiler from the mains supply at the external switch or isolator. 3) Never attempt to repair gas or sealed combustion components unless you are a qualified gas engineer. 4) Have a working carbon monoxide alarm installed and respond to any CO alarm as an emergency.

Initial homeowner checks (safe, basic):

1) Note the exact symptoms and timings. Record whether S.26 appears only during DHW calls, whether other fault codes appear, and whether the boiler still fires for hot water. 2) Perform a simple reset: press the boiler reset button and observe the start-up. If the code does not reappear, monitor for recurrence. 3) Check external vents and the flue terminal for obvious blockages (leaves, bird nest, ice). Clear only if safe to do so without climbing or removing components. 4) Check the condensate discharge (if external) for frost/blockage in cold weather and clear any visible local obstruction. 5) Ensure the boiler has normal electrical supply and the isolator/fused spur has not tripped.

Diagnostic steps you can carry out without opening the boiler (observe-only tests):

1) Create a DHW demand by opening a hot tap and watch the boiler sequence. Note whether the fan starts with the burner and whether it stops promptly after you shut the tap. 2) If the fan keeps running long after the burner is off, that reproduces the overrun. Listen for unusual fan noise (grinding, wobble) that suggests a failing motor. 3) Check the boiler display for any additional error codes or maintenance messages that appear alongside S.26. 4) If you can safely access the boiler exterior, check for loose plugs or connectors on any visible wiring harnesses (do not remove covers or unplug connectors while powered).

If basic checks do not fix the issue or the fault recurs:

1) Power down the boiler at the isolator and leave it off for a couple of minutes, then power on and test again. 2) If S.26 returns, do not attempt internal repairs unless you are qualified. Make a note of when the fault occurs, any accompanying codes, what you observed during your tests (fan noise, blocked flue, condensate issue). 3) Contact a qualified heating engineer (Gas Safe registered in the UK) and provide them with the boiler model, serial number, and the information you recorded. A competent engineer will typically inspect the fan assembly, test fan motor operation and speed control, check PCB outputs and sensor signals, verify wiring and connectors, and check for any flue/airflow constraints that might confuse the control logic.

Why call a professional and what they may do:

1) A professional will safely open the boiler, test the fan under controlled conditions, use instrumentation to check voltage/pulse outputs to the fan, and replace the fan motor or control PCB if required. 2) They will also check related components such as airflow sensors, tachometer input (if present), and the boiler control board. 3) Because fan replacement or electronics work involves electrical and combustion-system knowledge, these tasks should only be carried out by a qualified engineer to maintain safety and warranty.

Additional notes:

1) Do not repeatedly reset the boiler to clear the code if it keeps returning; this can mask a fault and may cause further damage. 2) Keep records of the fault occurrence and any service visit details for warranty and service-history purposes. 3) If you’re unsure about any step, or you find additional or worsening symptoms (loss of ignition, persistent error codes, smells, leaks), stop and call a qualified engineer immediately.