Boiler Error Codes Guide: What Fault Codes Mean
January 2026
Mend Your Home
Boilers
Is your boiler displaying an error code? Don't panic. Error codes are your boiler's way of telling you something needs attention. This guide explains the most common fault codes for popular boiler brands and what action you should take.
Important: Most boiler repairs require a Gas Safe registered engineer. Never attempt to repair gas appliances yourself. If you smell gas, leave the property and call the National Gas Emergency line: 0800 111 999
Quick Actions by Error Type
DIY Fix Possible
Low pressure, frozen condensate, reset needed
Call an Engineer
Ignition faults, sensor failures, fan errors
Urgent/Gas Smell
Gas valve errors, smell of gas - evacuate & call 0800 111 999
Worcester Bosch Error Codes
| Code | Meaning | Action |
|---|---|---|
| EA | Ignition failure - boiler failed to ignite | Call Engineer |
| E9 | Safety cut-out activated - overheating protection | Call Engineer |
| D5 | Low water pressure detected | DIY: Top up pressure |
| A1 | Condensate pipe blocked or frozen | DIY: Thaw pipe |
| C6 | Fan not running at correct speed | Call Engineer |
| E2 | NTC sensor fault (temperature sensor) | Call Engineer |
| CE | Pressure sensor fault | Call Engineer |
Vaillant Error Codes
| Code | Meaning | Action |
|---|---|---|
| F22 | Low water pressure / dry fire protection | DIY: Top up pressure |
| F28 | Ignition failure - unsuccessful start | Call Engineer |
| F29 | Flame lost during operation | Call Engineer |
| F75 | Pump/pressure sensor fault | Call Engineer |
| F61 | Gas valve control fault | Urgent: Call Engineer |
| F62 | Gas valve shut-off delay fault | Urgent: Call Engineer |
| F83 | No temperature rise when burner on | Call Engineer |
Baxi Error Codes
| Code | Meaning | Action |
|---|---|---|
| E119 | Low water pressure | DIY: Top up pressure |
| E133 | Ignition lockout - gas supply issue | Call Engineer |
| E125 | Circulation fault - pump issue | Call Engineer |
| E128 | Flame lost during operation | Call Engineer |
| E160 | Fan speed fault | Call Engineer |
| E168 | Multiple faults detected | Call Engineer |
Ideal Boiler Error Codes
| Code | Meaning | Action |
|---|---|---|
| F1 | Low water pressure | DIY: Top up pressure |
| F2 | Flame loss / ignition issue | Call Engineer |
| F3 | Fan fault | Call Engineer |
| L2 | Ignition lockout | Call Engineer |
| L6 | False flame detection | Call Engineer |
| LC | PCB communication error | Call Engineer |
Got an Error Code? We Can Help
Gas Safe registered engineers available across Crawley, Horsham, Redhill, Reigate and all West Sussex & Surrey
DIY Fixes You Can Try Safely
Low Pressure (Most Common)
If your boiler shows a low pressure error:
- Locate the filling loop (usually underneath the boiler)
- Open both valves slowly
- Watch the pressure gauge rise to 1-1.5 bar
- Close both valves
- Reset the boiler if needed
If pressure drops frequently, you may have a leak - call us to investigate.
Frozen Condensate Pipe
Common in cold weather - the outdoor condensate pipe freezes:
- Locate the condensate pipe (white plastic, goes outside)
- Pour warm (NOT boiling) water over the frozen section
- Use a hot water bottle held against the pipe
- Once thawed, reset the boiler
We can insulate your condensate pipe to prevent future freezing.
How to Reset Your Boiler
After fixing a simple issue like low pressure:
- Look for a reset button (usually marked with a flame symbol or "reset")
- Press and hold for 3-5 seconds
- Wait for the boiler to attempt ignition
- If the error returns after 3 reset attempts, call an engineer
Warning: If you've reset the boiler 3+ times and the error persists, stop trying and call a professional. Repeated resets can cause further damage.
When to Call an Engineer Immediately
Call Us Now If:
- You smell gas - Leave property, call National Gas Emergency 0800 111 999
- Boiler is making loud banging noises
- You see water leaking from the boiler
- The same error keeps returning after reset
- Error codes relating to gas valve or flame
- Boiler is very hot to touch or overheating
- Black marks or staining around the boiler
Frequently Asked Questions
How much does it cost to fix a boiler error code?
Repair costs vary depending on the fault. Simple fixes like pressure issues may just need a service call (from £80). Part replacements like sensors typically cost £150-£300 including labour. Major components like PCBs or heat exchangers can be £300-£600+. We always diagnose before quoting so you know the cost upfront. Costs shown are on average for an average 3 bed home.
Why does my boiler keep losing pressure?
If you're constantly topping up pressure, you likely have a leak somewhere in the system. This could be a leaking radiator valve, a small pipe leak, or a faulty pressure relief valve. It's important to find and fix the leak rather than just keep topping up. We can perform a pressure test to locate any leaks.
Should I replace my boiler if it keeps showing errors?
Not necessarily. Many error codes are easily fixed. However, if your boiler is 10+ years old and requiring frequent repairs, replacement might be more economical. As a rule of thumb: if a repair costs more than 50% of a new boiler, consider replacement. We can advise on the best option for your situation.
Can I fix an ignition error myself?
You should NOT attempt to fix ignition faults yourself as they involve gas components. Ignition errors can be caused by faulty electrodes, gas valve issues, or blocked burners - all of which require a Gas Safe registered engineer to diagnose and repair safely.
Don't Ignore Error Codes
Small problems become expensive repairs if left. Get your boiler checked by a Gas Safe engineer today.