Error 2965 B

Safety precautions:

1. If you smell gas, leave the property immediately and call the gas emergency number. Do not operate switches, appliances or the boiler.

2. If the boiler is showing an overheat or safety fault, stop using the heating and hot water and switch the boiler to standby or turn it off at the mains electrical isolator if safe to do so.

3. Do not attempt to open the boiler casing, work on gas pipes, or replace gas-carrying components yourself. Only a Gas Safe engineer should handle gas-side repairs.

Initial homeowner checks (simple, safe actions):

1. Note the exact error code and any other display symbols or messages. Photograph the display if possible for the engineer.

2. Try a controlled reset: follow the manufacturer method (press reset button for the recommended time or use the control dial reset position). Wait and observe whether the code returns. Do not repeatedly reset more than two or three times in a short period.

3. Check the central heating flow temperature setpoint in the boiler menu and lower it by 5–10 degrees if it is set very high. Restart and observe.

4. Check boiler water pressure on the gauge. Typical pressure is around 1.0–1.5 bar when cold. If the pressure is very low, top up to the correct pressure following the manual. If the pressure is too high, consult a professional.

5. Make sure thermostats, room stats and programmer controls are not commanding the boiler to run at maximum continuously. Reduce demand and test.

6. Ensure radiator thermostatic valves (TRVs) and lockshield valves are open and that radiator outlets are not closed. Cold radiators or many closed circuits can reduce flow and cause local overheating.

7. Bleed radiators to remove trapped air which can impede circulation. After bleeding, re-check system pressure.

8. Listen at the boiler with the heating on: can you hear the circulation pump running? If the pump is silent or making grinding noise, there may be a pump failure or seizure affecting flow.

Specific diagnostic steps you can try (safe, non-invasive):

1. After a reset, run the heating and monitor the flow temperature display. Note whether the temperature rises very quickly or overshoots the setpoint. A very rapid rise suggests a sensor fault or lack of flow.

2. If the pump appears not to be running, try to gently nudge the pump shaft only if the pump has an accessible manual run spindle and you are confident — otherwise stop and call an engineer. Never dismantle the pump.

3. Check the condensate pipe for blockage (frozen or blocked condensate can cause faults on some models). If the condensate is frozen in cold weather, thaw carefully with warm water or a warm cloth; do not use open flame.

4. If you suspect controls (room stat, external control) are commanding maximum temperature, isolate or turn them off temporarily to see if the boiler behaves differently.

5. Look for other related fault codes in the boiler log or display that might indicate a sensor short/open (codes like E2/E5 or F0 entries in other documentation). Loose sensor connectors can cause false over-temperature signals; if you are competent and the boiler is isolated electrically you may check that the wiring plugs to accessible sensors are pushed in, but do not disconnect gas or internal components.

When to call a professional:

1. If the error returns after a reset, or if you cannot find an obvious circulation issue or control fault, call a Gas Safe registered engineer.

2. Call a professional if you discover the pump is not running, if sensors or wiring appear damaged, if the HCM or control board error codes are present, or if you are asked to open the boiler casing to access components. These items require specialist testing and safe handling.

3. Call an engineer immediately if you see leaks, scorch marks, hear unusual noises from the burner, or if the boiler will not lock out and continues to overheat.

What to tell the engineer and what to prepare:

1. Provide the exact error code (2965 B), any other codes, and describe when the fault occurs (constant, on first fire-up, after radiator bleed, during hot water demand etc.).

2. Tell them what checks and resets you have already tried and the boiler pressure reading.

3. Have access to the boiler manual if available and any previous service history.

Final safety note:

Do not attempt repairs that involve gas connections, internal electrical components, or replacement of sensors, control boards, pumps or the HCM yourself. These tasks require a qualified Gas Safe engineer for safe and correct diagnosis and repair.