Guide
Boiler Fault Codes: When to Stop and Call a Professional
A UK-focused guide to knowing when a boiler fault has moved beyond safe user checks.
Last updated: 2 April 2026
Boiler fault codes often indicate pressure, ignition, sensor, or combustion problems. Some user checks are reasonable, but repeated faults should not be treated as a DIY repair project.
Stop and call a professional when
- The boiler repeatedly locks out after a standard user reset.
- You suspect a gas supply, ignition, or combustion issue.
- Pressure drops again quickly after topping up.
- Any step would require opening the boiler casing.
Related code pages
Worcester Bosch Boiler EA
The boiler has failed to ignite properly
Worcester Bosch Boiler A1
Water circulation or pump performance issue
Worcester Bosch Boiler C6
Fan, flue, or air pressure sensing problem
Worcester Bosch Boiler D1
Control board or internal communication fault
Worcester Bosch Boiler E9
The boiler has overheated or hit a high temperature limit
Worcester Bosch Boiler 224
System water pressure is too low
Worcester Bosch Boiler 227
System water pressure is too low
Worcester Bosch Boiler 229
The boiler has overheated or hit a high temperature limit
Worcester Bosch Boiler 232
Flame detection has been lost during operation
Worcester Bosch Boiler 233
Flame detection has been lost during operation
Worcester Bosch Boiler 268
Water circulation or pump performance issue
Worcester Bosch Boiler 281
A boiler sensor is giving an invalid reading
Worcester Bosch Boiler 286
Water circulation or pump performance issue
Worcester Bosch Boiler 295
A boiler sensor is giving an invalid reading
Worcester Bosch Boiler 296
Flame detection has been lost during operation
Worcester Bosch Boiler 297
Gas supply control or gas valve issue
Worcester Bosch Boiler CE
Fan, flue, or air pressure sensing problem
Worcester Bosch Boiler 208
A boiler sensor is giving an invalid reading
Vaillant Boiler F22
System water pressure is too low
Vaillant Boiler F23
System water pressure is too low
Vaillant Boiler F24
Water circulation or pump performance issue
Vaillant Boiler F27
Flame detection has been lost during operation
Vaillant Boiler F28
The boiler has failed to ignite properly
Vaillant Boiler F29
Flame detection has been lost during operation
Vaillant Boiler F32
Fan, flue, or air pressure sensing problem
Vaillant Boiler F54
Gas supply control or gas valve issue
Vaillant Boiler F61
Gas supply control or gas valve issue
Vaillant Boiler F62
Gas supply control or gas valve issue
Vaillant Boiler F64
A boiler sensor is giving an invalid reading
Vaillant Boiler F65
The boiler has overheated or hit a high temperature limit
Vaillant Boiler F67
Control board or internal communication fault
Vaillant Boiler F72
A boiler sensor is giving an invalid reading
Vaillant Boiler F75
Water circulation or pump performance issue
Vaillant Boiler F76
The boiler has overheated or hit a high temperature limit
Vaillant Boiler F77
Condensate, drainage, or pump protection issue
Vaillant Boiler F83
A boiler sensor is giving an invalid reading
Ideal Boiler F1
System water pressure is too low
Ideal Boiler F2
Flame detection has been lost during operation
Ideal Boiler F3
Fan, flue, or air pressure sensing problem
Ideal Boiler F4
The boiler has failed to ignite properly
Ideal Boiler F5
A boiler sensor is giving an invalid reading
Ideal Boiler F6
A boiler sensor is giving an invalid reading
Ideal Boiler F9
Water circulation or pump performance issue
Ideal Boiler HF
The boiler has failed to ignite properly
Ideal Boiler L1
The boiler has overheated or hit a high temperature limit
Ideal Boiler L2
The boiler has failed to ignite properly
Ideal Boiler L5
Control board or internal communication fault
Ideal Boiler L6
Flame detection has been lost during operation
Ideal Boiler C0
A boiler sensor is giving an invalid reading
Ideal Boiler C2
A boiler sensor is giving an invalid reading
Ideal Boiler C5
Fan, flue, or air pressure sensing problem
Ideal Boiler C6
Fan, flue, or air pressure sensing problem
Ideal Boiler C7
Control board or internal communication fault
Ideal Boiler D4
System water pressure is too low
Baxi Boiler E1
A boiler sensor is giving an invalid reading
Baxi Boiler E10
A boiler sensor is giving an invalid reading
Baxi Boiler E20
A boiler sensor is giving an invalid reading
Baxi Boiler E28
Condensate, drainage, or pump protection issue
Baxi Boiler E50
Control board or internal communication fault
Baxi Boiler E53
A boiler sensor is giving an invalid reading
Baxi Boiler E55
Control board or internal communication fault
Baxi Boiler E78
Control board or internal communication fault
Baxi Boiler E96
Control board or internal communication fault
Baxi Boiler E97
Control board or internal communication fault
Baxi Boiler E98
Control board or internal communication fault
Baxi Boiler 110
The boiler has overheated or hit a high temperature limit
Baxi Boiler 117
System water pressure is too low
Baxi Boiler 118
System water pressure is too low
Baxi Boiler 125
Water circulation or pump performance issue
Baxi Boiler 128
Flame detection has been lost during operation
Baxi Boiler 130
Fan, flue, or air pressure sensing problem
Baxi Boiler 133
The boiler has failed to ignite properly
Frequently asked questions
Can boiler fault codes usually be fixed at home?+
Only some pressure or user-reset situations are suitable for homeowner checks. Gas and internal boiler faults should be left to a qualified engineer.