Ariston boilers are known for energy efficiency and reliable performance, but like any modern heating system, they use built-in diagnostic codes to alert you when something isn’t working as it should. Understanding these Ariston boiler error codes can help you identify problems early, prevent damage, and know when it’s time to call a professional.
This guide explains the most common Ariston error codes, what they mean, and what you can typically do to fix or troubleshoot them.
1. Ariston Error 501 – Ignition Failure (Flame Not Detected)
What it means:
The Error 501 ariston appears when the boiler attempts to ignite but fails to detect a flame. This is one of the most common issues in Ariston boilers.
Possible causes include:
- No gas supply
- Faulty ignition electrode or flame sensor
- Low gas pressure
- Blocked burner or debris buildup
- Temporary ignition glitch
How to fix it:
- Restart the boiler using the reset button.
- Check your gas supply—make sure other gas appliances are working.
- Ensure adequate pressure (generally around 1.0–1.5 bar).
- If the error persists, a technician may need to clean the burner or check the ignition components.
When to call a professional:
If multiple resets fail or the boiler frequently shows Error 501, there may be an ignition or gas valve issue that requires expert attention.
2. Ariston Error 101 – Water Pressure Too High
What it means:
The boiler has detected an excessively high pressure level, which can be unsafe.
Possible causes:
- Overfilled system
- Faulty pressure relief valve
- Expansion vessel issue
Quick checks:
- Bleed a radiator to slightly reduce pressure.
- If the pressure rises again quickly, internal components may need inspection.
3. Ariston Error 108 – Low Water Pressure
What it means:
The boiler senses insufficient water in the system.
Common causes:
- Water leak in the system
- Recently bled radiators
- Faulty pressure sensor
Possible fixes:
- Refill the boiler using the filling loop until it reaches the correct pressure (1–1.5 bar).
- Inspect for visible leaks around radiators or pipes.
4. Ariston Error 5P1 / 5P2 – Circulation Problems
What it means:
The pump is not circulating water correctly.
Typical causes:
- Pump failure
- Blocked pipes or sludge
- Airlock in the system
Fix:
A professional may need to adjust or replace the pump, flush the system, or remove trapped air.
5. Ariston Error 304 – Flue Gas Temperature Issue
What it means:
The boiler has detected an abnormal temperature difference in flue gases.
Possible causes:
- Blocked flue
- Faulty flue gas sensor
- Incorrect installation angle
Solution:
A certified technician must inspect the flue system for obstructions or sensor failures.
6. Ariston Error 302 – Overheating Warning
What it means:
Water inside the boiler is too hot and has triggered a safety shutdown.
Causes may include:
- Pump failure
- Blockage in heat exchanger
- Thermostat malfunction
Fix:
Turn the boiler off and call an engineer—overheating issues should be handled professionally.
7. Ariston Error A01 – Ignition Lockout
What it means:
Similar to Error 501, but generally indicates repeated ignition failures leading to a safety lockout.
Possible causes:
- Gas supply issues
- Faulty ignition leads
- Burner problems
Fix:
Try a reset. If the code returns frequently, service is recommended.
8. Ariston Error E34 – Fan or Air Pressure Switch Issue
What it means:
The boiler cannot detect proper airflow through the combustion chamber.
Possible causes:
- Faulty fan
- Blocked air pressure tubes
- Air pressure switch failure
Fix:
Professional diagnosis is required because this relates to combustion safety.
When Should You Call a Professional?
While some error codes can be fixed with a simple reset or pressure adjustment, you should call a certified heating engineer if you notice:
- Error codes reappearing after resets
- Strange noises or smells
- Leaks, overheating, or complete ignition failure
- Any issue related to gas, combustion, or internal electrical components
Final Thoughts
Understanding common Ariston boiler error codes helps you respond quickly and safely when a problem occurs. Issues like Error 501 (Ignition Failure) are often easy to troubleshoot, but recurring or complex faults require professional help to ensure safety and long-term performance.
