Error E131

Safety precautions:

- If you smell gas, do not touch the boiler or any electrical switches. Get everyone out, ventilate the property if safe, and call the gas emergency number immediately.

- Before any inspection, switch the boiler to the OFF position and isolate electrical supply at the fused spur if possible. Do not attempt internal combustion or gas valve work unless you are a Gas Safe engineer.

- Do not remove covers that expose live electrical parts or gas/burner components unless you are qualified.

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

1) Note when the code appeared and whether it cleared after cooling. Record any pattern (happens after a long call for heat, during cold weather, etc.).

2) Try a simple reset: follow your boiler manual or press and hold the boiler reset button (usually 3–5 seconds). If the code clears and the boiler runs normally, monitor closely. If it returns, stop using the reset as a permanent fix.

3) Visually inspect the external flue terminal (outside the property). Look for obvious blockages: leaves, bird/wasp nests, rubbish, snow or ice. If you find debris you can safely remove (from outside), remove it; do not force anything down the flue.

4) Check the area around the boiler for adequate ventilation and that air inlets are not blocked.

5) Listen for the fan when the boiler tries to start. If the fan does not run or sounds unusual, note that for the engineer.

6) Check basic system circulation: is system pressure normal (around 1–1.5 bar cold for most systems)? Are radiators cold at the top (airlock) or is the pump humming? Bleeding radiators to remove trapped air can sometimes restore circulation and clear overheating faults. Re-pressurise only if you know how and if pressure is low.

Specific diagnostic/next steps (what an engineer will do or what else to try before calling if you are confident):

1) After a safe reset and the checks above, run the boiler and watch for recurrence. If E131 returns quickly, turn the boiler off and call a Gas Safe engineer.

2) If you found and removed an external blockage and the fault does not recur after reset, monitor for repeat occurrences (repeat blockages or nesting indicates need for a flue guard or engineer intervention).

3) If radiators were airbound and bleeding plus re-pressurising cleared the code, book a service to investigate why air entered the system (e.g., pump/applications, corrosion, or loose valves).

4) Do not attempt to adjust or bypass flue thermostats, open the burner box, or alter gas components. These actions require a qualified engineer.

When to call a professional:

- If resetting does not clear the code or if the code returns after a short time.

- If you cannot safely remove an external flue obstruction or you suspect internal flue blockage.

- If you suspect pump failure, circulation fault, fan failure, sensor or PCB faults, or any combustion/gas supply issue.

- Any repair that involves gas, burner, fan replacement, sensor replacement, PCB work or flue testing must be carried out by a Gas Safe registered engineer.

What the engineer will check and likely do:

- Perform flue flow/temperature and CO/combustion checks, inspect and clear any internal/external flue blockage, test and replace a faulty flue thermistor/thermostat if required, check fan operation and air supply, verify pump and circulation, check for overheating caused by poor circulation (airlocks, seized pump, closed valves), and inspect PCB fault history. They will also run the boiler under load to confirm the fault is fixed.

Final important notes:

- Treat E131 as a safety lockout. Temporary resets are fine as a diagnostic step, but repeated lockouts are a sign of a real fault that needs a qualified engineer.

- Never bypass safety devices or attempt gas-side repairs yourself. Call a Gas Safe registered engineer for persistent or unclear faults.