Ariston Excalibur 27 MFFI Excalibur 100 MFFI Fault codes & diagnostics

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

Combi Natural Gas 2004-2007 Discontinued
GC Number 47-116-31
No manual available yet We don't hold the official service manual for this model yet. We're sourcing it.

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Severity at a glance

Each cell = one fault code. Hover to identify.
7 High
Fault codes

All 7 documented codes

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E25 425

Your boiler has automatically turned itself off because it has detected that it is getting significantly too hot, which is a safety protection step.

High Engineer only £120-250 Shared across the Excalibur range

Parts commonly replaced

  • NTC sensor
  • Heat exchanger
  • Pump
Full explanation for E25 425
E61 567

Your boiler is failing to ignite because it cannot detect the spark required to start the flame safely.

High Engineer only £150-250 Shared across the Excalibur range

Parts commonly replaced

  • Ignition electrode
  • Ignition lead
  • PCB
Full explanation for E61 567
E61 569

Your boiler is failing to detect the flame correctly, so it has safely shut itself down to prevent gas from building up.

High Engineer only £120-220 Shared across the Excalibur range

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • PCB
Full explanation for E61 569
Ignition Failure

Your boiler is unable to light the gas burner to provide heating or hot water and has shut down for safety.

High DIY-safe £100-280 Shared across the Excalibur range

What to check first

  1. Check if other gas appliances, like a cooker, are working to ensure gas is reaching the property.
  2. Ensure your gas meter has credit if you use a pre-payment meter.
  3. Press the 'Reset' button on the control panel to attempt a restart.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Electrode
  • Printed Circuit Board (PCB)
Full explanation for Ignition Failure
Insufficient Circulation

Your boiler has stopped working because the water pressure inside your heating system has dropped too low to function safely.

High DIY-safe £80-150 Shared across the Excalibur range

What to check first

  1. Locate the filling loop (a silver braided hose) underneath the boiler.
  2. Open the valves at both ends of the loop to allow water into the system.
  3. Monitor the pressure gauge on the front panel and close the valves once it reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Pressure Relief Valve (PRV)
  • Expansion Vessel
  • Pressure Gauge
Full explanation for Insufficient Circulation
Insufficient System Pressure

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £0-120 Shared across the Excalibur range

What to check first

  1. Locate the flexible silver filling loop underneath or near your boiler.
  2. Slowly open the small tap(s) on the loop to allow water into the system.
  3. Watch the pressure gauge and close the taps firmly once it reaches 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve
Full explanation for Insufficient System Pressure
Overheating

Your boiler has shut down because it has detected that the water inside the system has become dangerously hot.

High DIY-safe £120-350 Shared across the Excalibur range

What to check first

  1. Locate the reset button (usually marked 'R') on the control panel and press it.
  2. Ensure all radiator valves are fully open to allow water to flow freely.
  3. Check that your system pressure is between 1.0 and 1.5 bar on the gauge and top up if necessary.

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Main Heat Exchanger (Descaling)
Full explanation for Overheating
Status & diagnostic codes

14 operating states & engineer diagnostics

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

164 225 Diagnostic Your boiler has detected a physical seal failure, which means gas or fumes could leak out, so you should turn it off immediately and stop using it. 164 229 Diagnostic Your boiler has detected a physical seal failure, likely causing a small water leak inside the appliance casing that needs to be addressed to prevent damage to internal electrical components. 164 261 Diagnostic Your boiler is signalling a fault with a internal seal which could lead to a water leak or pressure loss inside the unit. 164 282 Diagnostic Your boiler has detected a minor internal seal leak, which likely needs to be addressed to prevent water damage or further system failure. Anti-frost device Status Your boiler has detected that the water inside is getting too cold and has automatically turned on its internal heater to prevent the pipes from freezing. E61 468 Diagnostic Your boiler's built-in pressure management system is struggling, which can cause the internal pressure to rise too high and force the unit to shut down to prevent damage. E61 483 Diagnostic Your boiler has detected a leak within its internal water system, which is preventing it from running safely. E61 485 Diagnostic Your boiler has detected an issue with the control system that regulates the gas flow, meaning it cannot safely ignite or maintain a flame. E61 490 Diagnostic Your boiler is struggling to circulate water properly, which means it cannot move heat around your radiators or taps effectively. E61 520 Diagnostic Your boiler is struggling to accurately read or maintain the water pressure in your heating system, which is preventing it from firing up reliably. E61 547 Diagnostic Your boiler is having trouble managing the gas supply during startup and has safely shut down to prevent an unsafe ignition. E61 565 Diagnostic Your boiler is failing to ignite because it cannot detect the flame needed to heat your water or home. E61 665 Diagnostic Your boiler has detected an issue with its internal hardware settings regarding how it processes fuel, which is preventing it from lighting safely. E61 667 Diagnostic Your boiler has detected that it is incorrectly set up for the type of fuel it is currently receiving, which prevents it from operating safely.