Identifying error symbols on a boiler

Updated on 11th November 2026:

Kieran Haig

Technical Repair Engineer, British Gas

A symbol, warning light or error code can appear on your boiler when something needs looking at. But what they mean will depend on your boiler's make and model. This guide explains some common examples, what you can safely check and when to call an engineer.

What do the symbols on my boiler mean?

Boiler symbols are small icons that appear on most modern boiler displays to show the system status. They can vary between manufacturers, but most modern boilers use similar symbols. 

The table below shows some common boiler symbols and what they might mean. 

If your boiler is displaying an error code, you can use our Instant Expert tool to see if there’s anything you can do to help resolve the issue, or book an engineer to take a look.

What does a boiler error code mean?

Boiler error codes can signal various boiler problems, such as:

• Low water pressure 
• Overheating 
• Ignition problems
• A problem with the fan 
• Blocked air or flue fault

An error code doesn’t always mean you need an engineer. It may be something you can safely check yourself, like low pressure or a frozen condensate pipe. Always follow your boiler instructions and contact an engineer if you’re unsure.

Common boiler error symbols and codes

Low boiler pressure symbol

A low boiler pressure symbol means the pressure has dropped below the normal range. Your boiler can lose pressure for different reasons, from leaks in your central heating system to recently bled radiators. When it’s cold, the pressure gauge should sit between 1 and 1.5 bar. If it’s below 1 bar, you may be able to repressurise the boiler yourself by following the manufacturer’s instructions. If the pressure keeps dropping, or you don’t feel comfortable doing it, book an engineer visit.

Crossed-out or flashing flame symbol

A crossed-out or flashing flame icon often means there’s an ignition failure or a safety lockout. This could be due to:

• No gas supply
• Ignition failure
• A frozen condensate pipe 

Don’t try to repair any gas components yourself. Follow the reset instructions for your boiler if recommended. And if the fault remains, contact a Gas Safe registered engineer.

Overheating symbol

An overheating symbol could mean that your boiler’s too hot. This could be down to:

• Poor water circulation 
• A problem with the pump 
• Blockages 
• Other system faults 

If your boiler repeatedly overheats, get an engineer to look at it for you.

Frozen pipe symbol or error

A frozen pipe symbol or error could mean that your condensate pipe has frozen. This can happen during very cold weather if the pipe’s outside or in an unheated garage. You might also hear a gurgling noise or find that the boiler’s stopped working. If the pipe is safely accessible from ground level, you may be able to thaw it by placing a hot-water bottle against the pipe or pouring warm (not boiling) water over the frozen section. Once it’s thawed, check the manual to see if you need to reset the boiler.

Service or spanner symbol

The service or spanner symbol could mean:

• Your boiler’s due a service
• Your boiler needs maintenance
• Your boiler’s found an issue that needs looking at

Check the manual to find out what the symbol means for your make and model – and whether you need to arrange an engineer visit.

What should I do if my boiler shows an error symbol?

If your boiler shows an error symbol, you can follow these steps: 

1. Make a note of the symbol or code

Take a photo so you have a record of it.

2. Check the boiler manual

Look in the boiler manual or search for the exact make and model on the manufacturer’s website.

3. Check your heating and hot water

This will tell you if the boiler’s still working normally.

4. Check for common problems 

Check the pressure, gas and electricity supply, and if an external condensate pipe has frozen.

5. Reset the boiler if the instructions recommend it

Follow the steps for your exact make and model.

6. Get help if the error remains

Contact a Gas Safe registered engineer if the fault returns or you’re not confident carrying out the checks.

Can I reset my boiler when an error symbol appears?

You may be able to, but only if the instructions for your boiler recommend it. Different makes and models have different reset procedures, so follow the manufacturer’s instructions carefully.

Avoid repeatedly resetting the boiler, as this won’t fix the underlying problem. If the error keeps returning or the recommended reset doesn’t work, contact a Gas Safe registered engineer.

When should I call an engineer?

Contact a Gas Safe registered engineer if:

• The same error keeps returning
• The boiler repeatedly shuts down
• There’s no heating or hot water
• The pressure keeps dropping
• The boiler’s leaking
• There are unusual noises coming from the system 
• The boiler repeatedly overheats
• You think there’s a gas-related problem

If you smell gas or suspect a gas leak, open doors and windows, avoid flames and electrical switches, and contact the National Gas Emergency Service immediately on 0800 111 999. 

How to prevent boiler faults

You can help keep your boiler working properly by:

• Getting it serviced every year by a Gas Safe registered engineer
• Asking an engineer whether an external condensate pipe needs insulating
• Checking the pressure from time to time and repressurising it if needed 
• Bleeding radiators when they have cold spots
• Getting any problems, recurring warning symbols, leaks or unusual noises checked by a qualified engineer

Need help?

If the error’s still showing on your boiler or it isn’t working properly, our expert engineers can help get things working again.