Ariston Eurocombi A/23 MFFI Fault codes & diagnostics

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

Combi Gas 1999-2003 Discontinued
GC Number 47-116-10
Download the Ariston Eurocombi A/23 MFFI manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
24 High 2 Medium

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
47-116-10 Eurocombi A/23 MFFI 1999–2003

All 26 documented codes

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A 01

Your boiler has detected that it has become too hot and has automatically shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Overheat thermostat
  • NTC sensor
  • Primary heat exchanger
  • Pump

Related codes

A02

Your boiler has detected a problem with the fan that safely removes exhaust gases, meaning it has shut down as a safety precaution.

High Engineer only £180-350

Parts commonly replaced

  • Extraction Fan
  • Air Pressure Switch
  • Control PCB

Related codes

A03

Your boiler has failed to ignite the flame reliably and has stopped trying for your safety.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve
  • PCB

Related codes

A04

Your boiler is failing to create a spark to ignite the gas, meaning it cannot provide heating or hot water.

High Engineer only £100-£250

Parts commonly replaced

  • Ignition Electrode
  • Ignition Lead
  • Printed Circuit Board (PCB)

Related codes

A05

Your boiler is struggling to switch between providing hot water and heating your home due to a jammed internal mechanical part.

High Engineer only £160-280

Parts commonly replaced

  • Three-Way Diverter Valve
  • Diverter Valve Motor Actuator

Related codes

A06

Your boiler has stopped working because the water is not being pumped around the system properly.

High Engineer only £220-£450

Parts commonly replaced

  • Circulation pump
  • Pump capacitor
  • Main PCB

Related codes

A07

Your boiler is failing to detect the flame needed to heat your water, so it has shut down for safety.

High Engineer only £120-£280

Parts commonly replaced

  • Flame detection electrode
  • Ionisation probe
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

A08

Your boiler has detected an electrical safety issue or a component failure that prevents it from starting up safely.

High Engineer only £120-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Ignition Electrode
  • Wiring Harness

Related codes

A09

Your boiler is struggling to confirm that the burner has lit correctly, causing it to shut down for safety.

High Engineer only £120-280

Parts commonly replaced

  • Ionisation Probe
  • Printed Circuit Board (PCB)
  • Ignition Electrode

Related codes

A10

Your boiler has failed to detect a flame and has locked out to ensure your safety.

High DIY-safe £120-280

What to check first

  1. Check that your gas prepayment meter has credit
  2. Ensure other gas appliances in your home are working to confirm gas supply
  3. Press the 'Reset' button on the front of the boiler control panel

Parts commonly replaced

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

Related codes

Showing 11–20 of 26
A11

Your boiler's electronic control system has detected an internal electrical failure that prevents it from starting up safely.

High Engineer only £180-320

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Ignition Transformer

Related codes

A12

Your boiler has detected that water is not flowing through the system correctly, likely due to a blockage in the internal filter.

High Engineer only £90-180

Parts commonly replaced

  • System Filter
  • Central Heating Return Filter
  • Circulation Pump

Related codes

B01

Your boiler has switched itself off because it has reached an unsafe temperature and needs to cool down before it can be used again.

High DIY-safe £120-280

What to check first

  1. Turn off the boiler and allow it to cool for 20 minutes.
  2. Ensure all radiator valves are fully open and there is no air trapped in the system.
  3. Check that the system pressure is between 1.0 and 1.5 bar on the gauge.
  4. Press the Reset button on the control panel to restart the boiler.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger
  • NTC Temperature Sensor

Related codes

B02

Your boiler is not receiving a signal from your thermostat, which means your heating won't turn on even if you try to increase the temperature.

High DIY-safe £60-220

What to check first

  1. Check if your thermostat batteries need replacing.
  2. Ensure the thermostat is set to 'Heat' and the temperature is set higher than the current room temperature.
  3. Check that the wireless receiver near the boiler is powered on and has a light showing.

Parts commonly replaced

  • Thermostat batteries
  • Room thermostat unit
  • RF receiver

Related codes

B03

Your boiler's internal mechanism that controls the flame size has failed, meaning the system cannot regulate its heat output properly and has shut down for safety.

High Engineer only £140-£280

Parts commonly replaced

  • Gas Valve Modulator Coil
  • Complete Gas Valve Assembly
  • Main Control Board

Related codes

B05

Your boiler has detected a problem with the sensor that monitors the temperature of the water being sent to your radiators, which prevents it from heating your home safely.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating (CH) NTC Temperature Sensor
  • Sensor Wiring Loom

Related codes

B06

Your boiler has detected that the water pressure inside the system is too low for it to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver braided hose with small valves underneath the boiler).
  2. Slowly open the valves to allow water into the system while watching the pressure gauge.
  3. Close the valves firmly once the pressure gauge reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Low pressure switch
  • Filling loop valve

Related codes

B07

Your boiler is having trouble switching between heating your radiators and providing hot water because an internal switch is stuck or failing.

Medium Engineer only £120-220

Parts commonly replaced

  • Diverter Valve Microswitch
  • Diverter Valve Diaphragm
  • Complete Diverter Valve Assembly

Related codes

B08

Your boiler's built-in timer or clock has encountered a communication error, meaning the heating may not turn on at your scheduled times.

Medium DIY-safe £70-160

What to check first

  1. Check the clock settings to ensure they haven't been accidentally cleared
  2. Rotate the timer pins or digital settings to 'On' to see if the boiler fires
  3. Perform a simple reset of the boiler using the 'R' or reset button

Parts commonly replaced

  • Mechanical Timer Clock
  • Digital Programmer
  • Control PCB

Related codes

BOILER SHUTDOWN

Your boiler has switched itself off completely to prevent damage because a safety sensor has detected a problem with how it is operating.

High DIY-safe £100-350

What to check first

  1. Locate the reset button or dial on the front control panel.
  2. Press or turn the dial to 'Reset' for a few seconds and then release.
  3. Check if the system pressure gauge is between 1 and 1.5 bar; if low, top up using the filling loop.

Parts commonly replaced

  • Overheat Thermostat
  • Ignition Electrode
  • Printed Circuit Board (PCB)

Related codes

Showing 21–26 of 26
E02

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

High DIY-safe £80-120

What to check first

  1. Locate the filling loop, which is usually a metal braided hose underneath the boiler.
  2. Open the valves on the filling loop to allow cold mains water into the system.
  3. Watch the pressure gauge on the front of the boiler until it reaches 1.5 bar, then securely close the valves.

Parts commonly replaced

  • Pressure relief valve
  • Pressure gauge
  • Expansion vessel

Related codes

Ignition Lockout

Your boiler is unable to light the gas flame to provide heating or hot water, and has shut down as a safety precaution.

High DIY-safe £100-350

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to ensure gas supply.
  2. Verify that your prepaid gas meter has credit, if applicable.
  3. Press the Reset button on the control panel to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

INSUFFICIENT WATER

Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.

High DIY-safe £0-160

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath the boiler.
  2. Slowly open the one or two small taps on the loop until you hear water flowing.
  3. Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps tightly.
  4. Turn the selector switch to 'Reset' to clear the fault light.

Parts commonly replaced

  • Filling loop valve
  • Water pressure switch
  • Expansion vessel re-pressurisation

Related codes

L.E.D. D

Your boiler has detected that water is not moving through the system properly, which is preventing it from heating up safely.

High DIY-safe £100-£280

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is below 1 bar, use the filling loop underneath the boiler to top up the water levels.
  3. Ensure all radiator valves and internal isolation valves are fully open to allow water to flow.
  4. Reset the boiler once the correct pressure is reached.

Parts commonly replaced

  • Circulation Pump
  • Primary Pressure Switch
  • Automatic Air Vent
L.E.D. G

Your boiler has got too hot and has shut itself down as a safety precaution to prevent damage.

High DIY-safe £120-350

What to check first

  1. Wait 30 minutes for the system to cool down completely
  2. Check that all radiator valves are fully open to allow water flow
  3. Turn the selector switch to the 'Reset' position and then back to 'On'

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Main Heat Exchanger
Safety Shut-off

Your boiler has failed its internal safety check and has shut itself down to prevent a fault from becoming more serious.

High DIY-safe £180-450

What to check first

  1. Locate the Reset button on the control panel
  2. Press and hold the Reset button for five seconds
  3. Wait for the boiler to attempt to restart; if it fails again, do not continue to reset

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Ignition Electrode
  • Gas Valve

Related codes

7 operating states & engineer diagnostics

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