🔍 Common Boiler Fault Codes and What They Mean (By Brand)
Boilers are great—until they stop working and flash a confusing fault code at you.
Don't panic! These codes are your boiler's way of telling you something's wrong. In many cases, the issue is minor and easily fixed — if you know what the code means.
In this guide, we’ll cover:
- What boiler fault codes are
- Common issues they represent
- Quick fixes you can try
- When to call a Gas Safe engineer
- The most frequent fault codes for popular boiler brands
🧠 What Are Boiler Fault Codes?
Modern boilers come with a built-in digital display that shows fault codes (letters and numbers) when something’s wrong. These codes help identify the issue — from low pressure to ignition failure — without needing to take the boiler apart.
Each manufacturer has its own set of codes, but the underlying issues are often the same.
⚠️ Most Common Boiler Issues Behind Fault Codes
| Problem | Typical Cause | May Require a Professional? |
|---|---|---|
| 🔻 Low Water Pressure | Leak or radiator bleeding | Not always |
| 🔥 Ignition Failure | Gas supply issue or blocked burner | Yes |
| ❄️ Frozen Condensate Pipe | Cold weather, external pipe frozen | Not always |
| 🚿 No Hot Water or Heating | Diverter valve or sensor fault | Yes |
| 💨 Fan or Flue Problems | Blockage or faulty fan | Yes |
🔧 Common Boiler Fault Codes by Brand
🔹 Vaillant Boiler Fault Codes
| Code | Meaning | Quick Advice |
|---|---|---|
| F22 | Low water pressure | Re-pressurise boiler |
| F28 | Ignition failed | Check gas supply; reset boiler |
| F75 | Pressure sensor/pump fault | Likely needs engineer attention |
🔹 Worcester Bosch Boiler Fault Codes
| Code | Meaning | Quick Advice |
|---|---|---|
| EA | Flame not detected | Check gas & reset boiler |
| E9 | Overheating | Turn off boiler and call engineer |
| A1 | Low water pressure | Re-pressurise using filling loop |
🔹 Ideal Boiler Fault Codes
| Code | Meaning | Quick Advice |
|---|---|---|
| L2 | Flame loss or ignition fault | Check gas; reset boiler |
| F1 | Low water pressure | Top up system to 1.0–1.5 bar |
| F2 | Flame still present after shut off | Needs engineer inspection |
🔹 Baxi Boiler Fault Codes
| Code | Meaning | Quick Advice |
|---|---|---|
| E119 | Low system pressure | Re-pressurise system |
| E133 | Ignition or gas issue | Check gas & reset boiler |
| E160 | Fan fault | Likely needs engineer attention |
🛠️ Can You Fix a Boiler Fault Code Yourself?
Yes — sometimes. Here’s what you can usually do without professional help:
✅ Re-pressurise the boiler using the filling loop
✅ Reset the boiler using the control panel
✅ Thaw a frozen condensate pipe with warm water
✅ Check for power or thermostat issues
⚠️ Never open the boiler casing yourself unless you’re Gas Safe registered.
If the same code keeps appearing or your boiler shuts down repeatedly, it’s time to call a qualified heating engineer.
📈 Pro Tip: Keep a Fault Code Log
Make a note of:
- The exact code
- What the boiler was doing at the time
- Any changes to the system (like bleeding radiators or topping up pressure)
This info helps engineers diagnose issues faster — saving time and money.
📞 When to Call a Gas Safe Engineer
Call in a professional if:
- The boiler won’t reset or keeps locking out
- You suspect a gas supply issue
- You hear banging, gurgling or unusual noises
- You see leaks or error codes that don’t go away
A Gas Safe registered engineer can properly diagnose and safely fix deeper issues.
🏁 Final Thoughts
Boiler fault codes can be confusing, but they’re incredibly helpful once you understand what they mean. Knowing how to respond can save you from chilly mornings and unexpected repair bills.
Still unsure? Don’t take chances with your heating — or your safety.
📞 Need Help With a Fault Code?
At Gas-Go Heating, our local Gas Safe engineers are on hand to diagnose and fix boiler issues.
✅ Same-day service. ✅ Fixed pricing. ✅ Friendly, expert advice.
