ATAG Boiler Fault Codes Explained: Causes, Fixes, And When To Call An Engineer

Nothing disrupts home comfort like a boiler that suddenly stops working, especially when it flashes a confusing error code you don't recognise. If you own an ATAG boiler and it's showing a fault code on the control panel, you're not alone. Many London homeowners face this exact scenario, often in the middle of winter when the heating and hot water are most needed. 

The good news? Most ATAG fault codes are designed to alert you before a minor issue becomes a big problem. Whether it's an ignition failure, low pressure, or a sensor fault, this guide will help you understand what those codes mean and what you can do about them—safely and effectively. 

Are you experiencing persistent boiler errors? Don't wait until a minor issue turns into a full heating breakdown. Trust Maintracts Services to inspect, service, and repair your ATAG boiler efficiently. For fast, expert assistance with fault codes and heating diagnostics, contact our team today and get your home back to a comfortable state. Contact us on 020 8682 2244 or email info@maintracts.co.uk for expert advice and assistance. 

 

 

Common ATAG Boiler Error Codes

Fault Code	Meaning	Possible Cause	Action
133	Ignition failure	No gas supply, faulty ignition	Check the gas supply, reset the boiler
109	Low system pressure	Leak or insufficient top-up	Repressurise boiler
501	Fan fault	Faulty fan or blocked flue	Call engineer
103	Circulation fault	Airlock or pump failure	Bleed radiators or call a professional
104	The flow temperature is too high	Blocked system or sensor issue	Shut down the boiler, call the engineer
117	Overpressure	Overfilled system	Release pressure, monitor
110	Temperature sensor error	Sensor disconnected or faulty	The engineer needed to replace the sensor
607	Control panel communication	PCB or wiring fault	Professional diagnosis required

 

What Causes ATAG Boiler Fault Codes?

ATAG boilers, like any modern domestic heating appliance, are fitted with innovative diagnostic systems to detect internal issues. These errors appear on the boiler control panel as fault codes.

Common Causes Include:

• Ignition failure due to gas supply issues 
• Condensate pipe blockages, often from freezing temperatures 
• Low system pressure or airlocks in the central heating system 
• Faulty sensors in combi boilers or condensing boiler units 

Fault codes are designed to help you and your engineer quickly diagnose the root cause. However, they can appear confusing without some basic understanding. 

Read more: Glow worm boiler error codes and Baxi boiler error codes for keeping your indoors comfortable.  

 

How To Reset An ATAG Boiler After An Error

Many ATAG boiler error codes in the UK can be cleared with a simple reset, particularly if temporary conditions cause them.

Steps To Reset:

Identify the fault code on the display.

1. Refer to the manual or the official ATAG website for the meaning of the error code.
2. Press the reset button on the boiler control panel (usually marked).
3. Wait for the boiler to reboot. Observe if the error returns.

If the error persists, it's time for advanced heating system diagnostics or a professional visit.

 

Troubleshooting ATAG Boiler Problems At Home

Some issues can be safely checked and resolved at home, especially if you're familiar with the process.

DIY Checks:

• Is the boiler not heating? Ensure thermostat settings are correct and power is on.
• Low pressure? Top up the system to the recommended level (usually 1-1.5 bar).
• Ignition problems? Check that the gas supply is on and reset the boiler.

For any issues beyond these basic checks or repeated issues, such as fluctuating pressure or recurring fault codes, it is recommended to call a professional.

 

Trust Maintracts Services For Safe And Efficient ATAG Boiler Repairs

Boiler problems can quickly spiral into stressful and costly situations, especially if fault codes are ignored or misdiagnosed. At Maintracts, we don't just fix boilers—we restore comfort, confidence, and control. 

• Transparent solutions: We explain every step before we begin. 
• Rapid response: Ideal for recurring error codes and emergency faults. 
• Certified expertise: Gas Safe registered engineers with specialist knowledge of ATAG boiler systems. 
• Long-term reliability: From fault detection to annual servicing, we ensure your heating stays efficient year-round. 

Contact us on 020 8682 2244 or email info@maintracts.co.uk for expert advice and assistance. Get expert help exactly when you need it—without the guesswork.