British Gas RD 430i Fault codes & diagnostics

14 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 9.0 kW 2003 onwards Discontinued
GC Number 41-108-06
Download the British Gas RD 430i manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 10 High 3 Low
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-108-06 RD 430i System 2003–present
Just want the most common British Gas RD 430i faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 14 documented codes

Tap any card for details

2.4

Your boiler is temporarily pausing its operation to prevent the system from turning on and off too frequently, which protects the internal components from unnecessary wear and tear.

Low DIY-safe £0

What to check first

  1. Check that your room thermostat is set to the desired temperature.
  2. Ensure all radiator valves are open to allow heat to dissipate.
  3. Wait 15-20 minutes for the countdown timer to finish, as the boiler will likely restart automatically.

Related codes

Full explanation for 2.4
2.7

Your boiler is taking a short rest to prevent itself from turning on and off too quickly, which helps protect the internal parts from unnecessary wear and tear.

Low DIY-safe £0

What to check first

  1. Wait for 10-15 minutes for the countdown timer to finish
  2. Check that your room thermostat is set to a temperature higher than the current room temperature
  3. Ensure your radiator valves are open to allow heat to dissipate

Related codes

Full explanation for 2.7
b1

Your boiler's main control board cannot communicate with its security chip, preventing the system from starting.

High Engineer only £120-280

Parts commonly replaced

  • Code Chip
  • Main PCB (Printed Circuit Board)

Related codes

Full explanation for b1
C1

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

High Engineer only £180-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

Full explanation for C1
C4

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

High Engineer only £120-250

Parts commonly replaced

  • Air pressure switch
  • Venturi tube
  • Fan assembly

Related codes

Full explanation for C4
C6

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

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube

Related codes

Full explanation for C6
d3

Your boiler is not running because it cannot detect an essential electrical link required for it to start up.

High Engineer only £90-180

Parts commonly replaced

  • Main PCB
  • Wiring Link
  • Internal Fuse

Related codes

Full explanation for d3
E2

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.

High Engineer only £100-£180

Parts commonly replaced

  • Central Heating (CH) Flow Thermistor
  • Wiring Harness
  • Main Control Board

Related codes

Full explanation for E2
E9

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.

High DIY-safe £90-280

What to check first

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

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Thermistor

Related codes

Full explanation for E9
EA

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.

High DIY-safe £90-£350

What to check first

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

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve
  • PCB (Printed Circuit Board)

Related codes

Full explanation for EA
F7

Your boiler thinks it can see a flame inside the system even when it hasn't been told to start, causing it to shut down for safety.

High Engineer only £120-£350

Parts commonly replaced

  • Flame Sensing Electrode
  • Printed Circuit Board (PCB)
  • Gas Valve

Related codes

Full explanation for F7
FA

Your boiler is still sensing a flame even though it should have turned off, which is a safety concern that requires professional attention.

Emergency Engineer only £150-£400

Parts commonly replaced

  • Gas Valve
  • Ionisation Probe
  • Main Control Board

Related codes

Full explanation for FA
FC

Your boiler's internal control panel is unable to communicate with its main computer, meaning the system cannot display information or operate correctly.

High Engineer only £180-350

Parts commonly replaced

  • Display PCB
  • Main Control Board
  • Wiring Harness

Related codes

Full explanation for FC
Fd

Your boiler has gone into a temporary lockout mode because the reset button was held down or pressed when it wasn't necessary.

Low DIY-safe £0

What to check first

  1. Switch off the electrical power supply to the boiler at the fused spur switch.
  2. Wait for 30 seconds.
  3. Switch the power back on to clear the fault code and restart the boiler.

Related codes

Full explanation for Fd
Status & diagnostic codes

17 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

-II- Status Your boiler is currently running a routine startup sequence to fill its internal safety trap with water and is not actually faulty. 0.0 Diagnostic Your boiler is simply showing the record of the most recent error it encountered to help a service engineer diagnose past issues. 2.0 Status Your boiler is currently operating normally in it's standard heating or hot water mode, and this code is an status indicator rather than an error. 2.5 Diagnostic Your boiler has shut down because it thinks the water leaving the unit has become too hot, which is usually a sign of a circulation blockage or a sensor error. 5.0 Diagnostic Your boiler is currently running at its maximum capacity to bring your home up to the desired temperature and is not actually reporting a fault. 7.0 Diagnostic Your boiler's internal pump is not running at the correct speed to circulate water through your heating system properly. 30 Diagnostic Your boiler has likely experienced a failure in its internal software or electronic control board, meaning it cannot process the signals needed to heat your home. 40 Diagnostic Your boiler has detected an internal electronic failure or a communication error between its main control components. 50 Diagnostic Your boiler has detected an internal communication error between its main control components or a faulty sensor, meaning it cannot process the signals needed to provide heating. 60 Diagnostic Your boiler has failed to ignite or has lost its flame during operation, meaning it cannot provide heating or hot water until the issue is resolved. 70 Diagnostic Your boiler has detected a technical internal error, likely caused by a software glitch or a failure in the main control board, preventing it from starting up safely. 80 Diagnostic Your boiler has detected that the water temperature is too high, causing it to shut down to prevent damage or overheating. 90 Diagnostic Your boiler has detected an internal communication error between its electronic control boards, meaning it can no longer regulate the heating process safely. 100 Diagnostic Your boiler is potentially working too hard or experiencing a gas flow issue that exceeds its safe operating limits, leading to an automatic shutdown. P1 Status Your boiler is simply performing a routine startup check and will be ready to use in a few moments. P2 Status Your boiler is simply performing a routine safety check as it starts up, so please give it a few minutes to complete this process. P3 Status Your boiler is simply performing a routine internal check-up as part of its startup sequence.