Error S.6

Safety precautions:

- If you smell gas, evacuate the building immediately and call your gas emergency number — do not operate the boiler. If a CO alarm sounds, get everyone out and call emergency services and a Gas Safe engineer.

- Before doing any work isolate electrical power at the boiler isolator and, if you are unsure, turn off the gas supply at the meter. Do not attempt to work on gas or sealed combustion parts unless you are a Gas Safe registered engineer.

- If the boiler is making unusual noises, leaking, or there are flames/smoke from the flue, switch off the boiler and call an engineer immediately.

Initial homeowner checks (safe, no internal dismantling):

1. Note the error code, take a photo and record when it occurs and any recent events (power cuts, storms, servicing). This helps the engineer.

2. Reset the boiler once: switch off at the mains isolator or the boiler power button, wait 30–60 seconds, then switch back on and try to call for heat. Do not repeatedly reset more than 2–3 times.

3. Check external flue and air intakes: make sure the flue terminal and any air vents outside are clear of debris, nests, snow or leaves. A blocked flue can cause related faults.

4. Check room thermostat and programmer: ensure they are asking for heat when you expect the boiler to run. Turn the room thermostat up or set the programmer to call for heating to see if the fault appears immediately when demand starts.

5. Check the boiler pressure gauge is within the normal range (usually around 1–1.5 bar when cold for many systems). Extremely low pressure can cause other faults; top up only if you know how and the system instructions permit it.

Specific diagnostic checks and actions (if you are competent and confident with simple observations; do not open the boiler casing or touch live parts):

1. Reproduce the fault: after a reset, call for heating and watch the boiler. Note whether the fan starts, whether the burner ignites, and whether the fan continues to run after the boiler is attempting to shut down. Describe these behaviours for the engineer.

2. Listen for the fan: a noisy, grinding or obviously seized fan suggests mechanical failure and the unit will need service/repair.

3. Visual check of the flue run: any external obstruction or bird nest should be removed from the outside terminal only (do not reach into flue). If you clear a visible external blockage and the fault persists, turn the boiler back on and retest once.

4. Check for signs of wiring damage to any external controls you can safely access (room thermostat wires at the thermostat). Loose or shorted external control wiring can confuse the boiler into thinking the fan is overrun.

5. If you have basic electrical test skills and it is legal/safe to do so in your region, you can note whether the fan connector is plugged in (visual only) when the boiler casing is removed — but do not probe or disconnect live wiring. Preferably leave this to an engineer.

When to call a professional and what they will do:

- Call a Gas Safe registered engineer if the error persists after a single reset and the simple external checks above. Also call a pro if you hear grinding from the fan, see signs of electrical burning, smell gas, or there are repeated lockouts.

- A qualified engineer will safely isolate the boiler, remove the casing, and test the fan motor, hall sensor, fan connector and wiring harness with proper tools. They will check the flue gas temperature limiter (STB), the PCB inputs for the fan signal, and for any related error logs. They will clear and test for flue blockages internally and externally and may run electrical resistance and continuity checks on the fan and sensors.

- Likely technician repairs include cleaning or replacing the fan, repairing or replacing damaged wiring/harness connectors, replacing a faulty hall sensor or replacing/fixing the main PCB if it is at fault. They will also fully test the boiler for safe operation.

Important notes:

- Do not attempt to repair or replace fan motors, sensors, wiring inside the boiler, or the PCB yourself unless you are a Gas Safe registered engineer. Working on gas appliances or live electrical components is dangerous and illegal for unregistered persons in many jurisdictions.

- If the boiler repeatedly shows S.6 or other faults after an engineer visit, keep a record of occurrences, as persistent electronic faults often require component replacement or further diagnostic time.

- If in any doubt about safety, switch the boiler off and contact a Gas Safe engineer. Provide them with the error code, photos, and a description of what you observed during your checks to speed up diagnosis.