What do boiler error codes mean?

Understanding Boiler Error Codes

Modern boilers display error codes to help diagnose problems. Here are the most common codes by manufacturer:

Worcester Bosch Error Codes

• EA - Ignition failure (no flame detected)
• E9 - PCB fault or communication error
• A1 - Low water pressure (needs repressurising)
• D5 - Sensor fault
• C6 - Fan speed fault

Vaillant Error Codes

• F22 - Low water pressure
• F28 - Failed ignition attempts
• F29 - Flame lost during operation
• F75 - Pressure sensor fault
• F27 - Flame detected when shouldn't be (gas valve issue)

Baxi Error Codes

• E133 - Gas supply problem or ignition fault
• E119 - Low water pressure
• E125 - Circulation problem (pump or blockage)
• E168 - No signal from flame sensor
• E110 - Overheat protection activated

Ideal Error Codes

• F1 - Low water pressure
• F2 - Flame loss
• L2 - Ignition lockout
• L8 - Sensor fault
• FD - Fan fault

What You Can Try

For Pressure Errors (F22, E119, F1, A1):

1. Check pressure gauge (should be 1-1.5 bar)
2. Top up via filling loop if low
3. Reset boiler and try again

For Ignition Errors (F28, EA, E133, L2):

1. Check gas supply is on (other appliances working?)
2. Reset boiler by pressing reset button
3. If persists after 3 resets, call an engineer

When to Call a Professional

• Error code persists after reset
• Same error keeps recurring
• Error code not listed or unknown
• Any error involving gas supply or flames

NK Gas Services engineers are trained on all major boiler brands. Call 07404 922458 for same-day diagnostics in Wolverhampton, Walsall, and Cannock.