Ariston boiler error codes
12 codes that Ariston publishes for its boilers, each with what it means, the likely cause, what you can safely check and when to call a Gas Safe registered engineer. Tap your code:
Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone. Anything else is for a Gas Safe registered engineer. If you smell gas, call the National Gas Emergency Service on 0800 111 999. Codes that need one are marked Gas Safe engineer.
Read this first
Ariston’s UK user manual for the E-Combi ONE and E-System ONE sorts faults into two kinds. A safety shut-off clears by itself once its cause goes away; low water pressure, code 108, is the one you fix yourself by refilling. An operation shutdown (the codes in its error table) stays until you press RESET. The display shows “Err” and the number, such as Err / 501; the Alteas ONE Net shows the same numbers with a description, such as “Fault 501 – No flame detected”. This page follows the E-Combi ONE table and adds 110 from the Alteas ONE Net manual.
108 Water pressure too low
- What it means
- Insufficient water pressure in the heating circuit: the boiler has made a safety shut-off. The Alteas ONE Net shows “Fault 108 – Filling Needed”.
- Likely cause
- Water lost from the heating system.
- What you can safely check
Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone.
- Refill with the filling loop under the boiler: open it and press the MODE button for 5 seconds (the display shows PURGE); when the pressure gauge reads 1 bar, close the filling valve and press MODE again.
- When to call a Gas Safe registered engineer
- If you have to refill often, Ariston says to switch the boiler off, turn its external electrical switch off, shut the gas valve and have a qualified technician — a Gas Safe registered engineer — check for water leaks.
Source: Ariston, E-Combi ONE and E-System ONE user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
101 Overheating
- What it means
- The boiler has overheated and made an operation shutdown.
- Likely cause
- The manual names the fault only.
- What you can safely check
Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone.
- Press the RESET button. For safety the boiler allows at most 5 resets in 15 minutes.
- When to call a Gas Safe registered engineer
- If it comes back after several resets, contact a qualified technician — for a gas boiler, a Gas Safe registered engineer — or Ariston on 0333 240 8777.
Source: Ariston, E-Combi ONE and E-System ONE user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
103 104 105 106 107 Insufficient circulation
- What it means
- The heating water is not circulating well enough. The E-Combi ONE table prints 103 to 107 against this one description; the Alteas ONE Net calls it “Flow Check Failed”.
- Likely cause
- Too little water moving through the boiler.
- What you can safely check
Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone.
- Read the pressure gauge; if it is low, see 108.
- Press the RESET button. For safety the boiler allows at most 5 resets in 15 minutes.
- When to call a Gas Safe registered engineer
- If it comes back after several resets, contact a qualified technician — for a gas boiler, a Gas Safe registered engineer — or Ariston on 0333 240 8777.
Source: Ariston, E-Combi ONE and E-System ONE user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
501 No flame detected
- What it means
- The boiler did not detect a flame and has shut down; it does not restart on its own.
- Likely cause
- The manual names the fault only.
- What you can safely check
Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone.
- Press the RESET button. For safety the boiler allows at most 5 resets in 15 minutes.
- When to call a Gas Safe registered engineer
- If it comes back after several resets, contact a qualified technician — for a gas boiler, a Gas Safe registered engineer — or Ariston on 0333 240 8777.
Source: Ariston, E-Combi ONE and E-System ONE user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
305 306 307 Circuit board error
- What it means
- An error of the boiler’s printed circuit board (P.C.B.).
- Likely cause
- The boiler’s control board.
- What you can safely check
Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone.
- Press the RESET button. For safety the boiler allows at most 5 resets in 15 minutes.
- When to call a Gas Safe registered engineer
- If it comes back after several resets, contact a qualified technician — for a gas boiler, a Gas Safe registered engineer — or Ariston on 0333 240 8777.
Source: Ariston, E-Combi ONE and E-System ONE user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
110 Flow probe damaged
- What it means
- The Alteas ONE Net shows “Fault 110 – Send Probe Damaged”: the flow (“send”) temperature probe is damaged. It is a safety shut-off, which clears by itself if the cause goes away.
- Likely cause
- A damaged temperature probe.
- What you can safely check
Nothing for the owner to check: this one is for a Gas Safe registered engineer.
- When to call a Gas Safe registered engineer
- Gas Safe engineer If the boiler still shows the safety shut-off, Ariston says to switch it off, turn its external electrical switch off, shut the gas valve and contact a qualified technician — a Gas Safe registered engineer.
Source: Ariston, Alteas ONE Net user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
A code that is not listed here
Other Ariston models may use other numbers; the manual for your model is the authority. For a fault that happens often, Ariston says to contact an authorised service centre.
We list only codes the source below states. If your code is not here, it may belong to a model the source does not cover: your model’s manual is the authority.
Related pages
Source
Every code on this page comes from these pages, published by Ariston and read on the date shown. Meanings are written in our own words; nothing is taken from other makes, other models or third-party code sites.
- Ariston: E-Combi ONE and E-System ONE user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.
- Ariston: Alteas ONE Net user’s manual (GB/IE): appliance shut-off conditions, operation shutdown error table Checked 2026-09-29.