The most common Ariston boiler error codes include 108 for low water pressure, 101 for overheating, 501 showing no flame detection, and ignition problems like 5P1 or 5P2. These often stem from everyday issues such as air in the system or minor pressure drops, but recurring faults can mean your boiler is nearing the end of its reliable life.
If you live in the North West, Yorkshire or the Midlands and your Ariston boiler has started flashing a code, you are not alone. Many homeowners and landlords contact us at Clever Energy Boilers every week worried about these alerts. The good news is that most can be sorted with simple checks, while others point to the need for expert help.
Ariston Boiler Error Codes: A Quick Overview
Ariston boiler error codes provide a straightforward way to diagnose what is happening inside your heating system so you can act fast and keep your home comfortable.
| Error Code | Description |
| 101 | Overheating in the central heating circuit |
| 102 | Pressure sensor error (specific models) |
| 103 | Insufficient circulation |
| 104 | Insufficient circulation |
| 105 | Insufficient circulation |
| 106 | Insufficient circulation |
| 107 | Insufficient circulation |
| 108 | Low water pressure (request to fill) |
| 109 | System pressure too high |
| 110 | Flow temperature probe fault |
| 501 | No flame detected |
| 5P1 / 5P2 | Failed ignition attempts |
| 301–307 | Printed circuit board (PCB) faults |
| A41 | Fan fault |
| E43 | Air pressure switch fault |
Ariston Boiler Error Codes: Causes & How to Fix
Ariston boiler error codes each point to a specific part of your system that needs attention, so you can tackle the problem safely and get your heating back on track quickly.
Error Code 101: Overheating
When your Ariston boiler displays error code 101 it means the water temperature inside the central heating circuit has risen too high and the boiler has shut down to protect itself.
Common causes include air trapped in the radiators, a blocked or sluggish pump, closed valves on the flow or return pipes, or a build-up of sludge in older systems. Low system pressure can also trigger this fault because the water circulates less effectively.
Here is how to fix it step by step:
- Turn the boiler off at the mains and let it cool for at least 15 minutes.
- Bleed all your radiators starting from the top of the house to release any trapped air.
- Check the pressure gauge on the boiler – it should sit between 1 and 1.5 bar when cold.
- Top up the system pressure using the filling loop if it is too low (instructions are usually on the boiler front panel).
- Restart the boiler and listen for the pump running smoothly.
- If the code returns straight away, call a Gas Safe registered engineer to check the pump and heat exchanger.
Error Code 108: Low Water Pressure
Error code 108 on your Ariston boiler tells you the system does not have enough water pressure to operate safely, which is one of the most frequent faults we see in homes across the North West and Yorkshire.
It is usually caused by a slow leak in the pipework or radiators, a faulty pressure relief valve, or simply the pressure dropping naturally over time.
Follow these steps to fix it:
- Locate the pressure gauge on the front of the boiler.
- If it reads below 1 bar, find the filling loop (a flexible silver hose with two valves).
- Open both valves slowly until the gauge reaches 1.2–1.5 bar, then close them tightly.
- Check all visible pipework and radiator valves for damp patches or drips.
- Press the reset button on the boiler and test the heating.
- If the pressure drops again within a day or two, book a professional leak detection service straight away.
Error Code 501: No Flame Detected
Error code 501 appears when your Ariston boiler cannot detect a flame after attempting to ignite the burner, meaning your hot water and heating stop working.
Possible causes are a temporary gas supply interruption, dirty ignition electrodes, a faulty gas valve, or problems with the flame sensor.
Try these safe steps:
- Check that your gas meter and boiler isolator valve are fully open.
- Press the reset button once and watch whether the boiler attempts to ignite.
- If it fails again, turn everything off and wait 30 seconds before trying once more.
- Do not keep resetting repeatedly – this can damage components.
- Contact a Gas Safe engineer immediately if the code persists, as they can clean or replace the electrodes safely.
Error Codes 5P1 and 5P2: Ignition Failure
Codes 5P1 and 5P2 mean the boiler has failed to light the burner after one or two attempts and has locked out to prevent unsafe operation.
This often happens because of low gas pressure, blocked condensate pipe in cold weather, or worn ignition parts that are common in boilers over seven years old.
Here is what to do:
- Check your gas supply by trying another gas appliance in the house.
- If you are in the Midlands or Yorkshire and temperatures have dropped below freezing, gently thaw any external condensate pipe with warm water (never use a naked flame).
- Reset the boiler using the button on the front panel.
- If the fault returns after two resets, stop and call for professional help to avoid any risk with the gas supply.
Error Codes 301 to 307: Printed Circuit Board Faults
Error codes in the 301–307 range indicate a problem with the printed circuit board that controls all the boiler’s functions.
These faults are often caused by electrical surges, dampness inside the boiler, or simply the board reaching the end of its working life after years of daily use.
You cannot fix a PCB yourself, but follow the steps below:
- Note down the exact code shown.
- Power the boiler off at the mains for five minutes then back on to see if the code clears.
- If it returns, arrange for a qualified engineer to inspect and replace the board if needed.
- In the meantime, avoid using the heating to prevent further electrical strain.
Error Code A41: Fan Fault
Error code A41 shows that the fan, which helps remove dangerous gases through the flue, is not working correctly.
Causes include a seized motor, blocked flue outlet, or wiring issues that develop over time.
Safe troubleshooting steps include:
- Switch the boiler off completely.
- Visually check the flue terminal outside for any bird nests or debris (do not remove anything yourself).
- Restart and listen for the fan spinning up.
- Persistent A41 faults nearly always need an engineer to test and replace the fan unit.
Error Code E43: Air Pressure Switch Fault
Code E43 tells you the air pressure switch that monitors safe flue operation has detected a problem.
It can be triggered by a blocked flue, faulty switch, or fan not reaching the right speed.
The fix process is:
- Turn the boiler off and check the flue for blockages you can see from outside.
- Reset the boiler after five minutes.
- If the code returns, a Gas Safe engineer must test the pressure switch and fan together.
Persistent Ariston boiler error codes often mean your current unit is working harder than it should, leading to higher energy bills and the risk of sudden breakdowns when you need heat most.
Ready to Ditch Costly Repairs? Request Your Free Boiler Quote from Clever Energy Boilers Today
If your Ariston boiler keeps throwing up the same error codes, it could be a sign that repairs are only a short-term fix and your system is approaching the end of its lifespan. Replacing an ageing boiler with a modern, efficient model can cut your heating costs, improve reliability and give you peace of mind with a full manufacturer warranty.
At Clever Energy Boilers we specialise in expert boiler installation throughout the North West, Yorkshire and the Midlands. Whether you are a homeowner in Manchester fed up with cold mornings or a landlord in Birmingham needing compliant heating for tenants, our friendly team will guide you through the best options with no obligation. Request your free boiler quote today and let us help you enjoy consistent warmth without the worry of recurring fault codes.
Frequently Asked Questions
How often should I service my Ariston boiler to prevent error codes appearing?
Annual servicing by a Gas Safe registered engineer is the best way to keep error codes at bay. A thorough check cleans components, tests pressure and spots small issues before they turn into big faults, especially important for landlords who must meet legal safety standards.
Can freezing weather in Yorkshire or the North West make Ariston boiler error codes more likely?
Yes, cold snaps often cause condensate pipes to freeze, triggering ignition or pressure faults. Keeping the pipe insulated and knowing how to thaw it safely can stop many winter breakdowns before they start.
Is it ever worth repairing an Ariston boiler that shows the same error code repeatedly?
If the boiler is less than eight years old and the repair is straightforward, it can be cost-effective. For older units with PCB or fan faults, the parts and labour often add up to more than half the price of a new energy-efficient model.
Do landlords in the Midlands need to take extra steps when Ariston boiler error codes appear?
Absolutely. Landlords must ensure gas safety and provide working heating under tenancy rules. Getting a professional diagnosis quickly keeps you compliant and your tenants happy.
What should I do if my Ariston boiler loses power and then displays an error code when it restarts?
Power cuts can confuse the control board. Simply reset the boiler once the electricity returns. If the code stays on after two attempts, note it down and contact an engineer rather than keep resetting.
