Common problems guide

The most common British Gas RD 430i problems

The faults most likely to send a British Gas RD 430i into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
14 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common 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 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 EA
03
C1 High Engineer

Your boiler has stopped working because the fan isn't blowing air and fumes through the system as fast as it should.

Est. cost
£180-£450
Parts
Fan assembly, Printed Circuit Board (PCB), Air pressure switch
Full guide for C1
04
C4 High Engineer

Your boiler has detected that a safety sensor is stuck, preventing the fan from starting up correctly to clear away waste gases.

Est. cost
£120-250
Parts
Air pressure switch, Venturi tube, Fan assembly
Full guide for C4
05
C6 High Engineer

Your boiler's internal fan is working, but the safety system cannot detect enough air flowing through the flue to safely start the burner.

Est. cost
£120-280
Parts
Air Pressure Switch, Fan Assembly, Venturi Tube
Full guide for C6
06
E2 High Engineer

Your boiler has detected a problem with the sensor that monitors the temperature of the water heading to your radiators, causing the system to stop working for safety.

Est. cost
£100-£180
Parts
Central Heating (CH) Flow Thermistor, Wiring Harness, Main Control Board
Full guide for E2
Parts most often replaced

on the British Gas RD 430i

Overheat ThermostatCirculation PumpThermistorIgnition ElectrodeFlame Sensing ProbeGas Valve

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The British Gas shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 14-code list for the British Gas RD 430i

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →