Worcester Bosch Fault Codes
Check our list of Worcester Bosch error codes to find out what the fault indicates and what steps you can take next.
Not sure what your Worcester Bosch boiler error means? Check our list of Worcester Bosch fault codes to find out what the fault indicates and what steps you can take next.
Worcester Bosch fault codes list
Seeing an error or fault code on your Worcester Bosch boiler isn't a reason to worry. These codes exist to help you (or your engineer) work out exactly what's causing the problem. Below is a complete list of Worcester Bosch fault codes, along with what each one means and the steps you can take to fix it.
Worcester Bosch A7 fault code
The hot water (cylinder) temperature sensor has failed or lost its signal.
Possible cause:
- Loose or damaged wiring at the hot water sensor
- Hot water sensor itself has failed
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch E9 fault code
The safety temperature limiter has tripped, shutting the boiler down to protect it from overheating.
Possible cause:
- Little or no water moving through the system
- Fault with the flow or return temperature sensor, or its wiring
- Circulation pump not working properly
- Diverter valve stuck or blocked
- Water pressure sensor has failed
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch H07 fault code
System water pressure has dropped too low for the boiler to run safely.
This is one of the most common Worcester Bosch fault codes.
Possible cause:
- Little or no water in the system
- Small leak somewhere in the pipework or radiators
- Water pressure sensor faulty or its wiring loose
- Automatic filling valve has failed
- Internal expansion vessel has failed
How to fix it:
You can try topping up the pressure yourself using the filling loop until the gauge reads around 1 to 1.5 bar. If the pressure keeps dropping, or the fault won't clear, this needs an expert.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch E2 fault code
There's too great a difference between the flow and return temperatures, or the flow sensor has developed a fault. (Closest verified match — some Worcester Bosch ranges log this differently, so check your model's display against the manual too.)
Possible cause:
- Air trapped in the system
- Flow or return sensor wiring loose or damaged
- Flow or return sensor itself has failed
- Pump blocked or running with reduced output
- Diverter valve stuck or blocked
- Internal expansion vessel has failed
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch FA fault code
The boiler has detected a flame signal when the burner should be off.
Possible cause:
- Gas valve not sealing properly
- Fault on the control board
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch EA 227 fault code
The boiler tried to ignite but couldn't detect a flame.
This is one of the most common Worcester Bosch fault codes.
Possible cause:
- Frozen condensate pipe blocking the boiler from firing
- Gas isolation valve turned off
- Gas supply pressure too low
- Air in the gas line, common after first start-up
- Wrong gas type configured
- Blocked air intake
- Ignition or flame sensing electrode worn or dirty
- Burner itself faulty
- Condensate pump (where fitted) has failed
- Gas valve assembly faulty
- Damaged wiring harness or poor earthing
- Flue blockage or recirculation of exhaust gases
- Ignition transformer disconnected or faulty
- Control board faulty
How to fix it:
Check the condensate pipe isn't frozen and that the gas supply is on, then try one reset. If the fault comes straight back, this is a case for an expert.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch EA 229 fault code
The boiler lost its flame mid-operation and then failed to reignite.
Possible cause:
- Gas supply interrupted
- Flue blockage or recirculation of exhaust gases
- Poor earthing
- Blocked air intake
- Misfiring ignition
- Condensate pump (where fitted) has failed
- Burner faulty
- Damaged wiring harness
- Ignition electrode worn or damaged
- Gas valve assembly faulty
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch F0 fault code
An internal control board error, where the boiler's electronics aren't completing their checks within the expected time.
Possible cause:
- Faulty wiring connection to the gas valve assembly
- Control board (PCB) has failed
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch F7 fault code
A delay was detected in the flame switching off properly. (Closest verified match — this differs slightly from a straightforward "flame while off" fault, so an engineer may see it labelled differently depending on your model.)
Possible cause:
- Gas valve faulty
- Control board (PCB) has failed
- Ignition electrode worn or damaged
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
Worcester Bosch A1 fault code
The system pressure isn't rising as expected when the pump starts, pointing to a pump or airlock issue.
Possible cause:
- Water pressure sensor has failed
- Internal pump has failed or seized
- System pressure too low
- Internal expansion vessel has failed
- Little or no water in the system
- Air trapped in the system
- Break or fault in the internal wiring harness
How to fix it:
This is a case for an expert. Don't try to solve it yourself as it can be dangerous.
To solve it just call us on 01275 878000 or click here to contact us. We can solve your issue.
What to Do If You See a Worcester Bosch Fault Code
Before calling an engineer, it's worth trying a few simple checks, like topping up the boiler pressure or doing a single reset. But if the Worcester Bosch fault code keeps coming back, it's time to get a Worcester Bosch Accredited Installer out before it causes further damage.
Worcester Bosch Guarantee
Often yes, but it comes down to what caused the fault and whether your boiler is still within its Worcester Bosch guarantee period.
- Covered:
Where the fault traces back to a manufacturing defect or a component failing under normal use, Worcester Bosch will generally repair or replace the part at no cost. - Not Covered:
Problems stemming from poor installation, missed servicing, limescale, system sludge, frozen pipes, or accidental damage fall outside the guarantee. - Important:
Your guarantee only stays valid if the boiler is installed and serviced every year by a Gas Safe Registered engineer, ideally one accredited by Worcester Bosch (such as a Worcester Bosch Accredited Installer).
Call Gas Safe Heating Experts
When your Worcester Bosch boiler shows a fault code, it can be tempting to try a quick fix — but calling in a qualified engineer means your system gets diagnosed and repaired safely, without guesswork. Here's why:
- Experienced Diagnosis
Our engineers have years of hands-on experience with Worcester Bosch boilers and know how to read a fault code correctly, tracing it back to the actual root cause rather than just clearing the display. - Quality Parts
We fit genuine or manufacturer-approved parts, so your repair holds up long-term and doesn't put your existing warranty at risk. - Safe, Efficient Repairs
All work is carried out to Gas Safe standards, getting your heating back up and running without cutting corners. - Ongoing Support
Beyond the repair, we're on hand for servicing and maintenance to help stop the same fault coming back.
Serving Homes Across North Somerset
From coastal towns like Weston-super-Mare, Portishead, and Burnham-on-Sea to thriving communities such as Nailsea, Yatton, and Backwell, we diagnose, service, and fix Worcester Bosch fault codes right across North Somerset.
With over a decade of local experience, we know the region's homes inside out — from modern developments to traditional countryside cottages. Our team of Gas Safe Registered Heating engineers deliver trusted, high-quality workmanship tailored to each property's unique heating needs.
Contact us today for friendly advice or a free quote from our North Somerset boiler experts.