Ariston Genus 27 RFFI Fault codes & diagnostics

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

Regular Natural Gas 27 kW 1998-2005 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 27 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 properly and has locked itself out for safety.

High DIY-safe £90-280

What to check first

  1. Check if your gas supply is active (e.g., check other gas appliances)
  2. Locate the reset button (usually marked 'R' or 'Reset') on the control panel
  3. Press and hold the reset button for 2-3 seconds to restart the ignition sequence

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 switched itself off because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a flexible silver hose) underneath the boiler.
  2. Slowly open the one or two small valves on the loop until you hear water flowing.
  3. Watch the pressure gauge and close the valves tightly once it reaches 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • 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 itself 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 to allow water to circulate.
  2. Ensure your system pressure is between 1.0 and 1.5 bar on the pressure gauge.
  3. Turn the boiler off and on again (reset) after allowing it to cool down for 20 minutes.

Parts commonly replaced

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