Boiler Fault Codes Explained
What the code on your boiler means, whether it is safe to try a reset, and when to book a repair. Worcester Bosch, Vaillant, Ideal, Baxi, Potterton and Glow-worm, from Gas Safe registered engineers across Dunfermline and Fife.
Before you read any further
A fault code is the boiler telling you it has stopped itself for a reason. Most are harmless and some you can clear yourself. A few mean the boiler must not be used.
you can smell gas, the flame is yellow or orange rather than blue, or anyone in the house has headaches, dizziness or sickness that eases outside. That is the National Gas Emergency Service. Turn the boiler off, open windows and do not use the boiler until it has been checked.
Everything else on this page falls into two groups. Try this first means a reset, a pressure top up or thawing a pipe is safe for you to do. Engineer needed means the fault is inside the boiler or on the gas side, and by law only a Gas Safe registered engineer can work on it.
Worcester Bosch fault codes
Greenstar boilers show a letter and number code on the display. These are the ones we see most.
EA229 / D5Frozen condensate pipeTry this first
What it means: the plastic waste pipe outside has frozen and the boiler cannot drain, so it has locked out. The most common winter call we get in Fife.
- Find the white plastic pipe running from the boiler to an outside drain.
- Pour warm, not boiling, water along the frozen section, or hold a hot water bottle against it.
- Reset the boiler. If it clears, insulate the pipe before the next cold snap.
A1 / E9Low water pressureTry this first
What it means: the pressure gauge has dropped below the boiler's minimum, usually under 0.5 bar.
- With the heating off and the system cold, open the filling loop slowly until the gauge reads between 1 and 1.5 bar.
- Close both valves fully and reset the boiler.
- If it drops again within days there is a leak or a fault on the expansion vessel. Book a repair visit.
EA / EA227Ignition failure, no flame detectedEngineer needed
What it means: the boiler tried to light and could not, or lost the flame. Try one reset. If it comes back, stop.
Causes range from a gas supply problem to worn electrodes, a blocked flue or a failed gas valve. Check the hob lights, then book a repair visit. If you can smell gas, call 0800 111 999 first.
C6 / C7Fan faultEngineer needed
What it means: the fan that clears the flue gases is not running at the right speed, so the boiler will not fire. A safety component, and one for the engineer.
Vaillant and Ideal fault codes
ecoTEC, ecoFIT, Logic and Vogue boilers.
Vaillant F22Low water pressureTry this first
Top up to between 1 and 1.5 bar using the filling loop, then reset. Check the gauge weekly through winter; if it keeps dropping, book a repair.
Vaillant F28 / F29Ignition failure or flame lossEngineer needed
The boiler cannot light or keeps losing the flame. One reset is fine. If it returns, it needs a Gas Safe engineer: gas supply, electrodes, flue or gas valve.
Vaillant F75Pump or pressure sensor faultEngineer needed
The boiler cannot see a pressure change when the pump runs. Usually the pressure sensor or the pump itself. Engineer needed.
Ideal F1Low water pressureTry this first
Top up to between 1 and 1.5 bar and reset. Repeated drops mean a leak or expansion vessel fault.
Ideal F2 / L2Ignition lockoutEngineer needed
Check the hob lights, try one reset. If it comes back, book a repair visit. Do not keep resetting.
Ideal F3Fan faultEngineer needed
A safety component that vents the flue gases. Engineer needed.
Baxi, Potterton and Glow-worm fault codes
Baxi and Potterton share codes. Glow-worm uses the Vaillant style F codes.
Baxi E119 / Glow-worm F22Low water pressureTry this first
Top up to between 1 and 1.5 bar and reset. If it keeps dropping, book a repair.
Baxi E28 / Glow-worm F1, F28, F29Frozen condensate or flue faultTry this first
In cold weather, thaw the outside condensate pipe with warm water and reset. If it happens when it is not freezing, the flue or fan needs checking by an engineer.
Baxi E133 / Glow-worm F3Ignition or fan faultEngineer needed
The boiler cannot light, or the fan is not proving. One reset only, then book a repair visit.
Baxi E110 / Glow-worm F25Overheat or circulationEngineer needed
The boiler is getting too hot because water is not moving through it. Bleed the radiators, check the pressure and let it cool. If the code returns, the pump, a valve or a blockage needs an engineer.
Winter in Fife: the two faults that fill our diary
Frozen condensate pipes
The white plastic pipe from the boiler to an outside drain freezes on the coldest nights and the boiler locks out. Thaw it with warm water, reset, and then have it insulated or rerouted inside so it does not happen again. We fit condensate pipe insulation on any visit.
Pressure dropping in the cold
Water contracts as it cools, so a system that was fine in September can sit below the boiler's minimum in January. Top up once. If you are topping up every week, there is a leak somewhere, and a repair visit finds it.
What you can do, and what you must not
- Check the pressure gauge: 1 to 1.5 bar when cold. Top up with the filling loop, then close both valves.
- Bleed radiators with the heating off, starting downstairs, then check the pressure again.
- Reset the boiler once. Hold the reset button for a few seconds and let it restart.
- Thaw a frozen condensate pipe with warm water.
- Check the timer, thermostat and that the boiler has power.
- Never remove the boiler casing.
- Never touch gas pipework, the gas valve or the flue.
- Never adjust the ignition or replace internal parts.
- Never keep resetting a boiler that keeps locking out.
Gas work is illegal unless carried out by a Gas Safe registered engineer. Our register number is 626544.
Code will not clear?
Send us a photo of the boiler display and your postcode on WhatsApp, or book a repair visit online. We will tell you what the fault is likely to be and when we can be there.
Do not use the boiler. Open windows, turn off the gas at the meter if you can, and call the National Gas Emergency Service on 0800 111 999. Then call us for the repair.
Fault code questions we get asked
My boiler shows a fault code. What should I do first?
Check the code on this page. If it is a low pressure or frozen condensate code, follow the steps and reset once. If it is an ignition, fan or overheat code, or the reset does not clear it, book a repair visit. If you smell gas, call 0800 111 999 before anything else.
Is it safe to keep resetting my boiler?
No. One reset is fine. If the fault comes straight back, the boiler is telling you something is wrong and repeated resets can make it worse. Book a repair.
How much is a repair visit for a fault code?
£120 inc VAT, paid when you book. That covers diagnosis and the repair where parts allow. Any parts are quoted before they are fitted. On the Home Care Boiler and Complete plans there is no call-out charge.
My boiler make is not listed. Can you still help?
Yes. Send us a photo of the display and the boiler's make on WhatsApp and we will tell you what the code means and whether to book. We repair all major makes.
Why does my boiler lose pressure in winter?
Water contracts as it cools, so the gauge drops. Top up once. If you are topping up every week, there is a leak or an expansion vessel fault and a repair visit finds it.
How do I stop the condensate pipe freezing?
Insulate the outside pipe with foam pipe lagging, or have it rerouted inside. We can do either on a service or repair visit.
Book a boiler repair in Dunfermline and Fife
- Book online
- theheatnetwork.co.uk/book
- Phone
- 01383 660098
- Message us a photo
- hello@theheatnetwork.co.uk
- Office
- Scotia House, 5 Dickson Street, Dunfermline, KY12 7SL
- Hours
- Mon to Fri, 9am to 5pm
