Ariston Alteas One Fault codes & diagnostics

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

Combi Natural GasLPG 24 kW 2023-present
GC Numbers 47-116-9147-116-9247-116-98
Download the Ariston Alteas One 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.
2 Emergency 12 High 6 Medium 1 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
47-116-98 ALTEAS ONE+ NET 35 3302395 2023–present
Just want the most common Ariston Alteas One faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 21 documented codes

Tap any card for details

1P4

Your boiler has detected that the water pressure is getting low and needs to be topped up to keep running properly.

Low DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually blue levers or a small pull-down tap) underneath the boiler.
  2. Slowly open the valve(s) until you hear water entering the system.
  3. Watch the pressure gauge on the display until it reaches 1.5 bar, then close the valves completely.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 1P4
3 05

Your boiler's central computer system is experiencing a communication error and has shut down to prevent further issues.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Full explanation for 3 05
3 06

The boiler's internal computer has encountered a critical communication error and needs to be reset or inspected by a professional.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Full explanation for 3 06
5 03

Your boiler has detected a flame when it should be turned off, which is a significant safety precaution that prevents the unit from starting until it is inspected.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • PCB (Main control board)
  • Flame detection electrode

Related codes

Full explanation for 5 03
5P5

Your boiler is struggling to detect a consistent supply of gas, which may cause it to fail to ignite or cut out during use.

Medium DIY-safe £100-280

What to check first

  1. Check that your gas meter has credit (if using a pre-payment meter).
  2. Ensure your external gas emergency control valve is fully open.
  3. Try to relight other gas appliances, such as a hob, to see if the gas supply is active throughout the home.

Parts commonly replaced

  • Gas Valve
  • Ignition Electrodes
  • Gas Meter Regulator

Related codes

Full explanation for 5P5
5P6

Your boiler is struggling to light its flame successfully on the first few attempts, which may eventually lead to it shutting down completely.

Medium DIY-safe £100-280

What to check first

  1. Check that your gas meter has credit (if on prepay)
  2. Ensure other gas appliances in your home, like the hob, are working correctly
  3. Press the 'Reset' button on the front control panel

Parts commonly replaced

  • Ignition Electrode
  • Detection Electrode
  • Gas Valve

Related codes

Full explanation for 5P6
7 11

Your boiler is struggling to accurately monitor the temperature of the water returning from your radiators, which may cause your heating system to work inefficiently or stop altogether.

Medium Engineer only £120-220

Parts commonly replaced

  • Return NTC sensor
  • Wiring harness

Related codes

Full explanation for 7 11
7 12

Your boiler is having trouble communicating with the temperature sensor for your secondary heating zone, which may prevent that part of your home from heating up properly.

Medium Engineer only £150-250

Parts commonly replaced

  • Zone 2 return sensor
  • Wiring harness

Related codes

Full explanation for 7 12
7 13

Your boiler is having trouble reading the temperature in one of your heating zones, which may cause that specific area to not heat up properly.

Medium Engineer only £120-220

Parts commonly replaced

  • NTC temperature sensor
  • Wiring harness

Related codes

Full explanation for 7 13
7 23

Your boiler has detected that the water temperature in one of your heating zones is higher than it should be, causing it to shut down for safety.

Medium Engineer only £120-250

Parts commonly replaced

  • NTC temperature sensor
  • Zone valve motor
  • Pump

Related codes

Full explanation for 7 23
Showing 11–20 of 21
8 03

Your boiler's computer is confused because it does not recognize the specific power settings or the internal configuration of the burner unit.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • Gas valve

Related codes

Full explanation for 8 03
8 04

Your boiler is failing to recognise an essential internal communication module or add-on component required for the system to operate correctly.

High Engineer only £120-250

Parts commonly replaced

  • External gateway interface
  • PCB communication module
  • Wiring harness

Related codes

Full explanation for 8 04
102

Your boiler is struggling to accurately detect the water pressure, which prevents it from running safely and efficiently.

High Engineer only £120-210

Parts commonly replaced

  • Pressure sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 102
108

Your boiler has lost water pressure and has shut down to prevent damage, meaning it simply needs to be refilled to the correct level.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually blue handles or a small plastic key) underneath the boiler.
  2. Slowly open the valves until you hear water entering the system.
  3. Watch the pressure gauge and close the valves tightly once it reaches 1.5 bar.
  4. The error code should clear automatically; if not, press the 'Reset' button.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Auto air vent

Related codes

Full explanation for 108
109

Your boiler has too much water pressure inside the system, causing it to shut down for safety.

Emergency DIY-safe £80-200

What to check first

  1. Check that the filling loop valves under the boiler are tightly closed.
  2. Bleed water from a radiator using a bleed key until the pressure gauge on the boiler falls back between 1 and 1.5 bar.
  3. Restart the boiler once the pressure is stabilised.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve (PRV)

Related codes

Full explanation for 109
110

Your boiler's main temperature sensor has failed or has a loose connection, meaning the system can't monitor how hot the water is and has shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Flow Temperature Sensor (NTC Probe)
  • Sensor Wiring Harness

Related codes

Full explanation for 110
116

Your boiler has detected that the safety sensor for an underfloor heating circuit has tripped to prevent the floor from overheating.

High Engineer only £90-180

Parts commonly replaced

  • Floor thermostat
  • Overheat limit thermostat
  • Wiring harness

Related codes

Full explanation for 116
118

Your boiler has detected a fault with the sensor that measures the temperature of the water being sent to your radiators, which means it cannot heat your home safely.

High Engineer only £110-180

Parts commonly replaced

  • Central heating flow NTC sensor
  • Wiring harness
  • Main circuit board (PCB)

Related codes

Full explanation for 118
501

Your boiler has tried to light several times but has failed to create a flame, meaning you currently have no heating or hot water.

High DIY-safe £100-350

What to check first

  1. Check if your home gas supply is active by testing another gas appliance like a hob.
  2. Verify that your gas prepaid meter (if applicable) has enough credit.
  3. If it is freezing outside, check that the white plastic condensate waste pipe is not frozen.
  4. Hold the 'Reset' button for five seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Spark Generator

Related codes

Full explanation for 501
502

Your boiler thinks it sees a flame even though the gas should be turned off, so it has shut down as a safety precaution.

High Engineer only £140-£350

Parts commonly replaced

  • Ionisation Probe
  • Gas Valve
  • Main Control Board

Related codes

Full explanation for 502
Showing 21–21 of 21
612

Your boiler’s fan is not spinning at the correct speed, which means it cannot safely move air and gas through the system to provide heating or hot water.

High Engineer only £180-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for 612
Status & diagnostic codes

1 operating states & engineer diagnostics

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

3P9 Diagnostic Your boiler is simply reminding you that its annual safety check and service are now due.
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