Question 1

What does Worcester Bosch fault code EA 338 mean?

Accepted Answer

EA 338 is an ignition lockout fault on Worcester Bosch boilers. The boiler attempted to ignite multiple times and failed to establish a stable flame. Common causes include a gas supply interruption, a worn spark electrode, or a gas valve fault. Reset once only — if it re-locks, call a Gas Safe engineer. Do not keep resetting, as this risks gas accumulation.

Question 2

What does Worcester Bosch fault code E9 mean?

Accepted Answer

E9 on a Worcester Bosch boiler means the safety temperature thermostat has operated — the boiler has overheated. Allow the boiler to cool for 20–30 minutes before resetting. Common causes include a seized pump, scale or sludge on the heat exchanger, or an air lock in the system. If it overheats again after resetting, call an engineer.

Question 3

What does Worcester Bosch fault code 227 mean?

Accepted Answer

227 on a Worcester Bosch boiler indicates low system water pressure. Repressurise using the filling loop (usually under the boiler — two valves and a braided hose) until the gauge reads 1–1.5 bar cold, then reset. If pressure drops again within days, there is a leak or a failed expansion vessel that needs investigating.

Question 4

What does Vaillant fault code F.22 mean?

Accepted Answer

F.22 on a Vaillant ecoTEC boiler means low water pressure — the system pressure has fallen below 0.5 bar. Use the filling loop to raise pressure to 1–1.5 bar when the system is cold, then reset. If the fault returns within a week, there is likely a slow leak or a failing expansion vessel.

Question 5

What does Vaillant fault code F.28 mean?

Accepted Answer

F.28 on a Vaillant boiler is an ignition failure lockout. The boiler failed to establish a flame after multiple ignition attempts. First check that other gas appliances are working — if they are, reset once and observe. If the boiler re-locks, a Gas Safe engineer is needed. Never reset more than once on an ignition fault.

Question 6

What does Vaillant fault code F.75 mean?

Accepted Answer

F.75 on a Vaillant boiler means the boiler did not detect a pressure change when the pump started, indicating the pump may be seized (common after summer) or the pressure sensor has failed. Check that the system pressure is correct (1–1.5 bar) and listen for the pump running. A heating engineer is needed to diagnose and repair.

Question 7

What does Baxi fault code E119 mean?

Accepted Answer

E119 on a Baxi boiler means low water pressure. Repressurise the system to 1–1.5 bar using the filling loop, then hold the reset button for 3 seconds. Monitor pressure over the next 24–48 hours — if it drops again, there is a leak or expansion vessel fault that needs professional attention.

Question 8

What does Ideal fault code L1 mean?

Accepted Answer

L1 on an Ideal Logic boiler is a low pressure lockout. Repressurise using the filling loop to 1–1.5 bar cold, then press the reset button. If L1 returns within a week, the system has an active leak or a failed expansion vessel — both need an engineer to fix.

Question 9

Why does my boiler keep losing pressure?

Accepted Answer

Rapid pressure loss (within hours or days) indicates an active leak — check all radiator valve connections and look outside for water discharging from the pressure relief valve pipe. Slow pressure loss over weeks usually means a failed expansion vessel. Topping up pressure regularly is not a fix — the underlying cause needs diagnosing by a heating engineer.

Question 10

Is it safe to reset my boiler multiple times?

Accepted Answer

No. You should only reset a boiler once if it shows a fault. Repeatedly resetting on an ignition fault risks flooding the combustion chamber with unburnt gas. If the boiler re-locks after one reset attempt, call a Gas Safe registered engineer.

Question 11

What is a boiler lockout?

Accepted Answer

A boiler lockout is a safety shutdown — the boiler has detected a fault condition and stopped operating to prevent damage or danger. Most lockouts can be reset once using the boiler's reset button. If the boiler locks out again after resetting, there is an underlying fault that requires an engineer. Common causes include ignition failure, low pressure, overheating, and fan faults.

Boiler fault code
diagnostic tool.

I have a fault code

I have a symptom

The 5 mistakes most plumbers make with their website.

Boiler fault codediagnostic tool.

I have a fault code

I have a symptom

The 5 mistakes most plumbers make with their website.

Boiler fault code
diagnostic tool.