COMMON MAIN BOILER ERROR CODES

Ever seen those cryptic codes flashing on your boiler and wondered what they mean? Those are boiler error codes, and while they might look confusing, they’re beneficial for identifying what’s wrong with your heating system. Think of them as your boiler’s way of asking for help — each code point corresponds to a specific issue that needs attention. 

In this guide, we’ll outline some of the most common Main boiler error codes, explain what they mean, and help you understand whether it's a quick fix or something you should leave to the expert.  

At Maintracts Services Ltd, we take the mystery out of boiler fault codes. Whether your boiler has lost pressure, failed to ignite, or is showing repeated error messages, our expert engineers are here to help. With decades of experience diagnosing and resolving issues across all major boiler brands, including Main, Baxi, Ideal, Glow-worm, and more, we’ll quickly pinpoint the problem and get your heating back on track. We’re experts at responding quickly and are committed to delivering safe and effective repairs. Call us today on 020 8682 2244 to schedule a visit to discuss your boiler-related concerns! 

 

 

What Does A Boiler Fault Code Mean?

Boiler fault codes are messages from your boiler that identify a fault or malfunction. These codes are part of the built-in diagnostic system, designed to help engineers (and sometimes homeowners) understand what has gone wrong.

Instead of randomly guessing what’s behind a breakdown, an error code provides a clue. For example, one code might indicate low water pressure, while another might highlight an ignition failure. Knowing these codes makes the troubleshooting process faster and often cheaper.

 

Common Boiler Error Codes Across Brands

While different boiler brands use slightly different code systems, many of the underlying issues are the same. Here are some of the most frequent boiler problems and the error codes associated with them:

1. Low Water Pressure

A drop in water pressure is one of the most frequent issues with domestic boilers. Without enough pressure, your boiler can’t operate efficiently—or at all. Here are the most common error codes: 

• Baxi Boiler Error Code: E118 
• Ideal Logic Boiler Error Code: F1 
• Glow-Worm Boiler Error Code: F22 

To resolve such errors, check the pressure gauge located on the front of your boiler. If the pressure is below 1 bar, you’ll likely need to top up the system using the filling loop. However, if the problem persists, you may have a leak or a faulty pressure relief valve. 

2. Ignition Failures

Your boiler needs to ignite to provide hot water and heating. If it can’t, you’ll be left in the cold. These are the most common error codes:

• Worcester Bosch Boiler: EA
• Baxi Boiler: E133
• Ideal Logic Boiler: L2
• Main Boilers Boiler: E168

For a quick fix, ignition issues can be due to gas supply problems, blocked condensate pipes, or faulty electrodes. While resetting the boiler may provide temporary relief, these issues typically require the expertise of a professional.

3. Water Circulation Problems

If hot water isn’t circulating properly, your home may experience uneven heating or no heat at all. This is often due to a pump failure or airlocks in the system, and the code it shows is as follows: 

• Vaillant Boiler: E256 
• Potterton Boiler Error Codes: E125 
• Main Boilers: E125 

To fix it, bleeding radiators and checking for blockages may help, but pump issues usually require technical servicing. 

4. Sensor Failures

Sensors monitor temperature, pressure, and the presence of flame. If they fail, the boiler won’t function correctly. Here are its error codes: 

• Ideal Logic Boiler Fault Codes: F2, F4 
• Viessmann Boiler: A4, 20 
• Main Boilers: E297 

To fix a faulty sensor, ensure to consult an expert heating engineer for professional services. These are not user-serviceable parts of the boiler.  

 

Brand-Specific Boiler Error Codes Breakdown

Let’s take a quick look at how different boiler brands communicate issues using their error codes.

1. Worcester Bosch Boiler Error Codes

• EA – Ignition or flame failure
• E9 – Overheating due to heat exchanger issues
• F28 – Communication or ignition problems
• C6 – Fan speed issues
• D1 – Sensor fault

2. Baxi Boiler Error Codes

• E117 – Water pressure is too high
• E118 – Low pressure
• E133 – Ignition failure
• E135 – Lockout from ignition
• E28 – Temperature sensor issue

3. Vaillant Boiler Error Codes

• F27 – Incorrect gas-air mixture
• F75 – Pump or pressure sensor fault
• E256 – Water circulation issue
• F28 – Ignition fault
• F62 – Gas valve stuck or slow to operate

4. Viessmann Boiler Error Codes

• 5C, 5D, 5E, 5F – Communication faults
• 10 – Outdoor temperature sensor shorted
• 18, D1 – Broken sensor wire
• A4 – Burner blockage or pump issue
• 20 – Fault with supply temperature sensor

5. Ideal Logic Boiler Fault Codes

• F1 – Low system pressure
• LF – Failed ignition
• LC / L2 – Lockout due to ignition
• F2 – Flame detection issue
• F4 – Temperature sensor problem

6. Potterton Boiler Error Codes

• E125 – Circulation fault
• E131 – Overheat fault
• E160 – Fan fault
• E119 – Water pressure is low
• E270 – Flame loss

7. Ariston Boiler Error Codes

• 501 – Ignition lockout
• 103 – High water temperature
• 104 – The flow temperature is too high
• 108 – Low system pressure
• 305 – Water sensor failure

 

Signs You May Need A New Boiler

Not all boiler issues are fixable—at least not cost-effectively. Here are some signs that it may be time to consider a replacement:

• Repeated Error Codes: If you frequently reset your boiler or experience recurring faults, it's likely nearing the end of its lifespan.
• Strange Noises: Clanking, banging, or whirring sounds may indicate severe internal damage.
• Rising Energy Bills: An inefficient boiler uses more gas to heat your home.
• Poor Performance: If it takes a long time to heat your home or the hot water is unreliable, your boiler may be malfunctioning.

 

How To Reset Your Main Boiler After A Fault Code?

Sometimes, clearing a minor error is as simple as resetting the boiler. Here's a general way to reset your Main boiler:

• Locate the reset button — it’s usually marked clearly on the control panel.
• Press and hold the button for about 5 seconds.
• Wait as the boiler restarts. This might take a minute or two.
• Check if the error code disappears and the boiler operates normally.

However, if the error reappears or you smell gas, turn off the boiler immediately and call our Gas-Safe registered heating engineer for emergency support.

Conclusion: It’s Time To Call A Professional

Some minor boiler issues can be handled by confident homeowners. But when it comes to more serious problems, especially those involving gas or electrical components, it’s essential to call in a qualified professional. Faults like ignition failures, low water pressure that won’t stay fixed, or recurring error codes are signs that something deeper might be wrong.

That’s where Maintracts Services Ltd comes in. Our Gas-Safe registered engineers are trained to diagnose and repair all types of boiler issues safely and efficiently. We work with all major brands, including Main, Baxi, Glow-worm, Ideal, and more. With fast response times, honest pricing, and years of experience, we make it easy to get your heating system up and running again. If your boiler is displaying an error code or simply not working as it should, call us on 020 8682 2244 to book a service or arrange an emergency repair right now!