Error E109

Safety precautions:

1. If you are not confident working near a boiler, stop and call a Gas Safe engineer. Do not attempt gas or flue related repairs yourself.

2. Before touching pipework or electrical parts, isolate the boiler power at the mains and switch off the boiler. Only restore power when instructed to test.

3. Wear gloves and eye protection if you drain or bleed water. Have a container and cloths ready for any water.

Initial checks a homeowner can do:

1. Check the boiler display and note E109 and any other codes. Try a basic reset using the boiler's reset button or following the manual’s reset procedure. Some faults clear after a reset if they were transient.

2. Check system pressure on the boiler gauge. Aim for around 1.0–1.5 bar when cold. If pressure is low, repressurise using the filling loop to the recommended pressure and re-check operation. Do not over-pressurise.

3. Check room thermostat/timers and demand. Make sure the boiler is being called to heat. If the boiler isn’t being asked to run, circulation won’t start.

4. Look at radiators: run central heating and feel radiators. If some radiators are cold at the bottom or cold at the top, there may be trapped air or poor flow.

5. Check visible valves: ensure the isolation valves on the boiler and pump (if accessible) and any manual zone valves are fully open. If you find a closed valve, open it and try again.

Specific diagnostic and DIY fix steps:

1. Bleed radiators: release air from radiators starting from the one nearest the boiler and working outwards. Use a radiator key and a cloth; stop bleeding when water flows steadily. This often clears airlocks that cause poor circulation.

2. Reset the boiler after bleeding and repressurising if needed. Observe whether circulation returns and the E109 clears.

3. Check the pump for signs of life: with the boiler powered on and calling for heat, listen for the pump running (a gentle hum) and feel the pump body (don’t touch hot parts). If it is completely silent or very hot, the pump may be seized or electrically faulty.

4. Gentle tap method: if the pump appears seized and you are comfortable doing a simple, non-invasive test, with the boiler isolated and cooled, you may try to free a stuck rotor by gently tapping the pump housing with a wood or plastic handle. Do not remove the pump cap or wiring unless you are qualified—this can be dangerous and will often invalidate warranties.

5. Check for blocked magnetic filter or debris: if you have a magnetic filter on the system and you are able to access it safely, isolate the filter, drain as required and inspect/clean the filter. If unsure, leave this to an engineer.

6. Check motorised zone valves: if your system has motorised zone valves, observe their operation when heating is called. If a valve is stuck closed, circulation to that zone will be prevented. Some valves have manual levers to open them temporarily.

7. If you have bled radiators, checked pressure and opened valves and the fault persists, note whether additional fault codes appear (for example E110 overheat) and when they occur (immediately, after a few minutes). This information helps an engineer diagnose pump failure, airlocks or sensor/PCB issues.

When to call a professional:

1. Call a Gas Safe registered heating engineer if the fault persists after basic checks (bleeding radiators, checking pressure, resetting) or if you suspect the pump is electrically faulty, seized, or the magnetic filter is full/blocked.

2. Call a professional immediately if you see multiple error codes, smell gas, see leakage from gas components, or the boiler repeatedly locks out.

3. Any work involving electrical wiring, removing sealed covers, replacing the pump, valves, heat exchanger or PCB, or anything affecting the gas supply must only be completed by a qualified engineer.

Final note: E109 commonly resolves after bleeding radiators, ensuring correct pressure and confirming valves are open. If it does not, do not continue to run the boiler—turn it off and arrange a Gas Safe engineer to prevent further damage.