Error 86

Safety first:

1) If you smell gas, evacuate the property and call the gas emergency service immediately; do not operate electrical switches or the boiler. 2) Turn off the boiler at the external isolator or the mains before attempting any inspection that requires opening the casing. Only qualified persons should remove the boiler casing or work on live electrical/gas components. 3) Do not repeatedly reset the boiler if the same fault returns — this can mask a developing failure and may be unsafe.

Initial homeowner checks (safe, simple checks you can do):

1) Note the exact code on the display (86 or E86) and any other codes shown. 2) Check the external flue terminal for obvious blockages (nests, leaves, snow, ice). Clear any obvious obstruction from the outside (do not push objects into the flue). 3) Listen when the boiler tries to start: do you hear the fan start-up or any unusual grinding/rumbling noises? 4) Check the boiler has power and gas supply: ensure the isolator is on, check other electrical supplies, and confirm other gas appliances are working or the gas meter has credit if on prepayment. 5) Try a controlled reset: press and hold the reset button per the boiler manual (usually 5–10 seconds). Observe whether the boiler attempts to start and whether the fault clears.

If the fault clears after reset and operation is normal, monitor the boiler. If the same fan-related fault reappears, call a Gas Safe engineer — intermittent faults often indicate a failing component.

Safe diagnostic and repair steps for a qualified engineer (what the engineer will typically do):

1) Verify the fault using the service mode and fault history on the PCB. 2) Observe fan operation during a start attempt: check for correct rotation, speed, unusual noise or vibration. 3) Inspect and test the flue thermistor/sensors and flue path for restrictions or temperature anomalies. 4) Check electrical supply to the fan motor (mains and controlled outputs) and measure voltages/currents with appropriate test equipment. 5) Check fan motor continuity and insulation, as well as for seized bearings or rotor issues. 6) Inspect wiring and connectors between the fan and PCB for corrosion, broken wires or loose connections. 7) If fan motor is faulty, replace the fan assembly with manufacturer-approved spare. 8) If wiring and fan are good but the fan control signal from the PCB is absent or incorrect, test PCB outputs and replace PCB if confirmed faulty. 9) After any repair or replacement, run full operational and safety checks, confirm flue temperatures and CO/CO2 where applicable, and clear the fault memory. 10) Record the repair in the service log and advise the homeowner on any follow-up checks.

When to call a professional:

- If the basic homeowner checks (flue clear, power/gas on, reset) do not clear the fault. - If the fan does not physically start, makes loud/unusual noises, or the fault is intermittent. - Any work that involves opening the casing, electrical testing on live circuits, gas components, or replacing parts must be performed by a Gas Safe registered engineer.

Remember: fan faults affect combustion safety. If in doubt or if the fault persists, stop attempting DIY fixes and book a Gas Safe engineer to diagnose and repair the boiler safely.