Appliance category hub
Boiler Fault Codes
Browse boiler fault codes by brand with conservative guidance on display meanings, safe user checks, and when to contact qualified heating or gas help.
Definitions can vary by model and region. Some codes remain unconfirmed; check the complete display, exact model and the page's sources before taking action.
Brands covered
4
Code pages
92
Code categories
12
Safety guidance
Keep user checks outside the casing and follow the exact model's instructions. Do not work on gas, combustion, flues, sealed components or internal electrics. In the UK, employ a Gas Safe registered engineer competent for the specific gas work; check the categories on their ID card.
Source: HSE guidance for gas appliance owners, checked 22 September 2026.
Browse by brand
Baxi boiler codes
20 boiler code pages with documented meanings, evidence limits and safe next steps.
Ideal boiler codes
18 boiler code pages with documented meanings, evidence limits and safe next steps.
Vaillant boiler codes
28 boiler code pages with documented meanings, evidence limits and safe next steps.
Worcester Bosch boiler codes
26 boiler code pages with documented meanings, evidence limits and safe next steps.
Selected code pages
Baxi Boiler E128
Frequent flame loss when the full code is E128
Baxi Boiler E28
Flue-temperature NTC circuit fault in the applicable Baxi table
Ideal Boiler F9
PCB fault on the documented Instinct2 models
Vaillant Boiler F22
Low water pressure
Vaillant Boiler F23
Excessive flow-to-return temperature difference
Vaillant Boiler F24
Boiler temperature rising too quickly
Vaillant Boiler F25
Flue-gas temperature too high
Vaillant Boiler F27
Flame signal detected with the burner off
Vaillant Boiler F28
No flame established during ignition
Vaillant Boiler F29
Flame lost during operation and re-ignition unsuccessful
Vaillant Boiler F32
Fan fault
Vaillant Boiler F75
Insufficient pressure change when the pump starts
Find a code in this category
Filter by brand, code category, severity/status, or code text. A label does not establish whether an appliance is safe to use.
92 of 92
Baxi E128
Not assessedFrequent flame loss when the full code is E128
flame loss
Baxi E28
Not assessedFlue-temperature NTC circuit fault in the applicable Baxi table
sensor
Ideal F9
Not assessedPCB fault on the documented Instinct2 models
pcb control
Vaillant F22
Not assessedLow water pressure
pressure level
Vaillant F23
Not assessedExcessive flow-to-return temperature difference
circulation
Vaillant F24
Not assessedBoiler temperature rising too quickly
circulation
Vaillant F25
Not assessedFlue-gas temperature too high
fan flue
Vaillant F27
Not assessedFlame signal detected with the burner off
ignition
Vaillant F28
Not assessedNo flame established during ignition
ignition
Vaillant F29
Not assessedFlame lost during operation and re-ignition unsuccessful
flame loss
Vaillant F32
Not assessedFan fault
fan flue
Vaillant F75
Not assessedInsufficient pressure change when the pump starts
circulation
Ideal C6
Not establishedMeaning unconfirmed; exact model documentation is required
unconfirmed
Worcester Bosch 110
Not establishedMeaning unconfirmed; exact model documentation is required
unconfirmed
Ideal F5
mediumReturn-thermistor fault in Ideal’s documented F5 guidance
sensor
Worcester Bosch 200
Operating statusHeating mode
operating status
Worcester Bosch 201
Operating statusHot-water mode
operating status
Worcester Bosch 202
Operating statusAnti-cycle mode
operating status
Worcester Bosch 204
Operating statusBoiler water above the target temperature
operating status
Worcester Bosch 208
Operating statusChimney-sweep demand
operating status
Worcester Bosch 268
Operating statusRelay test activated
operating status
Baxi 117
Not assessedHigh system pressure when the full display is E117
pressure level
Baxi 118
Not assessedLow system pressure when the full code is E118
pressure level
Baxi 125
Not assessedCirculation fault when the full code is E125
circulation
Showing the first 24 matches. Narrow the filters to find a specific code faster.
Code categories in this library
Counts refer to published code pages, not how often an appliance develops a fault.
sensor (21)
PCB and control (10)
unconfirmed (10)
ignition (9)
fan and flue (7)
overheat (7)
circulation (6)
operating status (6)
Brands in this appliance category
Baxi
20 boiler code pages
Ideal
18 boiler code pages
Vaillant
28 boiler code pages
Related guides
Boiler Fault Codes: When to Stop and Call a Professional
First separate an emergency from a routine fault. A code needs the exact model and full display; it cannot by itself establish a safe reset or identify a part to replace.
When to Call an Appliance Engineer
Use the exact manual for permitted owner checks. Recurring faults, unsafe symptoms and work inside the appliance need appropriate professional help; emergencies need immediate action.
Why Your Boiler Keeps Losing Pressure
Use the pressure target and filling instructions for your exact boiler and installation. Repeated pressure loss needs investigation; a low reading alone does not identify a failed component.