Common problems guide

The most common British Gas boiler problems

The faults we see most often across the British Gas range — with plain-English causes, what to check first, estimated repair costs, and whether it's a DIY job or needs a Gas Safe engineer. Based on fault-code data across 2 British Gas boiler models.

24 unique codes
2 models covered
2 DIY-safe (top 8)
8 engineer needed

The most common British Gas faults

01
E9 High DIY-safe

Your boiler has switched itself off because it has become too hot internally, usually due to a lack of water flow or a circulation problem.

What to try first

Check if your radiator valves are open to allow water to flow.Check your boiler pressure gauge and top it up to 1.5 bar if it is too low.Press the reset button on the front of the boiler.

Est. cost
£90-280
Parts
Overheat Thermostat, Circulation Pump, Thermistor
Full guide for RD 430i E9
02
EA High DIY-safe

Your boiler is failing to light the gas or isn't staying lit, meaning you won't have any heating or hot water until it is reset or repaired.

What to try first

Check that your gas meter is turned on and gas is reaching other appliances like a hob.If you have a pre-payment meter, ensure you have sufficient credit.Press the Reset button on the front of the boiler for five seconds.

Est. cost
£90-£350
Parts
Ignition Electrode, Flame Sensing Probe, Gas Valve
Full guide for RD 430i EA
03
F78 High Engineer

Your boiler has lost communication with its external controls or internal wiring kit, preventing it from heating your home.

Est. cost
£90-180
Parts
Main PCB, Intelligent Wiring Kit, Wiring Harness
Full guide for 330+ F78
04
F3 High Engineer

Your boiler has detected that the internal component responsible for clearing exhaust gases is not operating correctly, so it has safely shut down to prevent any unsafe buildup.

Est. cost
£180-350
Parts
Fan assembly, Fan harness, PCB
Full guide for 330+ F3
05
F4 High Engineer

Your boiler is lighting up, but the flame is cutting out shortly after, meaning your heating and hot water will not stay on.

Est. cost
£150-300
Parts
Flame rectification probe, Gas valve, Ignition lead
Full guide for 330+ F4
06
F5 High Engineer

Your boiler has detected that it is running too hot and has automatically switched itself off to prevent any damage.

Est. cost
£120-250
Parts
Pump, NTC Thermistor, Heat Exchanger
Full guide for 330+ F5
07
F6 High Engineer

Your boiler is struggling to read the temperature of the water flowing to your radiators, so it has turned itself off to prevent overheating.

Est. cost
£120-200
Parts
Flow NTC Thermistor, Wiring Harness
Full guide for 330+ F6
08
F10 High Engineer

Your boiler's internal sensor that monitors the water temperature returning from your radiators has lost its connection, causing the system to stop heating to prevent damage.

Est. cost
£120-220
Parts
Return NTC thermistor, Wiring harness
Full guide for 330+ F10
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2 British Gas boilers with full fault code lists.
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Related guides

Losing pressure → Keeps cutting out → No hot water → When to replace → All guides →