Expert Guide to Worcester Bosch Boiler Fault Codes

Most Common Worcester Bosch Boiler Fault Codes

Here’s a breakdown of what those fault codes mean — and what to do next.

EA – No Flame Detected

Cause: The boiler tried to ignite but didn’t detect a flame.
Common reasons in Wokingham:

• Gas valve issues

• Frozen or blocked condensate pipe (especially during cold snaps)

• Flue or ventilation blockage

Fix:

1. Check the gas supply

2. Defrost the condensate pipe (if needed)

3. Press the reset button once

Still flashing? Book an Appointment— it could be a faulty ignition electrode or gas valve.

E9 – Overheat Lockout

Cause: The boiler has overheated.
Likely reasons:

• Sludge in system

• Pump failure

• Sensor issues

Fix:
Try resetting the boiler. If the fault returns, we may need to power flush your system or replace a faulty component.

A1 – Low Water Pressure

Cause: The pressure in your heating system has dropped too low.
How to fix it:

1. Check the pressure gauge (ideal is 1.0–1.5 bar)

2. Use the filling loop to top up pressure

3. Reset the boiler

If this keeps happening, you may have a leak or a faulty pressure sensor — we can help.

How to Reset Your Worcester Bosch Boiler

Resetting your Worcester Bosch boiler is usually simple.

Steps:

1. Find the reset button on the boiler fascia

2. Press and hold it for 3–5 seconds

3. Wait for the boiler to restart

Only reset once. Multiple resets indicate an underlying issue that needs professional attention.

Most Common Worcester Boiler Repairs in Wokingham

At Thermo-Tec, these are the top Worcester Bosch faults we repair:

• Frozen condensate pipes (especially in exposed pipework)

• Sludge in radiators causing overheating or banging

• Old diverter valves sticking (no hot water)

• Pressure drops due to leaks in older systems