Ariston Genus 15 RFFI Fault codes & diagnostics

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

Regular Natural Gas 15 kW Discontinued

The fault code is already on your display

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

Just want the most common Ariston Genus 15 RFFI faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

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(B) LED turning on

Your boiler has failed to ignite the gas burner and has shut down as a safety precaution.

High DIY-safe £120-300

What to check first

  1. Check that your gas supply is active (e.g., check other gas appliances or pre-payment meter credit)
  2. Locate the reset button (usually marked 'R') on the control panel and press it
  3. Ensure there are no external blockages to the flue pipe outside your home

Parts commonly replaced

  • Ignition electrode
  • Flame sensing probe
  • Gas valve
  • Printed Circuit Board (PCB)
Full explanation for (B) LED turning on
(D) LED turning on

Your boiler has detected that the water pressure is too low to operate safely and has shut itself down as a precaution.

High DIY-safe £0-120

What to check first

  1. Locate the internal or external filling loop (braided silver hose) under or near the boiler.
  2. Slowly open the valve or valves to allow water into the system until the pressure gauge reaches 1.5 bar.
  3. Close the valves tightly and check if the 'D' LED has turned off; you may need to press 'Reset'.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Expansion vessel
Full explanation for (D) LED turning on
(G) LED turning on

Your boiler has sensed it is getting too hot and has shut down as a safety precaution to prevent damage.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open (TRVs turned to max).
  2. Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar).
  3. Press the 'Reset' button on the control panel to see if the fault clears.

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Main Heat Exchanger
Full explanation for (G) LED turning on