Experiencing issues with your BAXI boiler? This comprehensive guide incorporates the latest official documentation for both the modern Baxi 600/800 & Combi 2 ranges and the classic Duo-tec/Platinum series. Whether you are seeing a cryptic code like E168 or a simple pressure fault, this guide will help you decide if it's a quick DIY fix or if professional help is required.
Understanding your boiler's language is the first step to a warm home. BAXI boilers are designed to "lock out" (shut down) safely when they detect a risk to the internal components or your safety. Our guide breaks these codes down into manageable actions.
Modern Series: Combi 2, System 2, 600 & 800
The newer generation of Baxi boilers utilizes a more granular error reporting system. These codes often appear as A.xx or E.xx on the digital display. Ensure you are reading the code correctly before proceeding.
| Error Code | Fault Description | Troubleshooting / Meaning | Action |
|---|---|---|---|
| A.02.06 | Low System Pressure | Water pressure is below 0.5 bar. Repressurise system to 1.5 bar using the filling loop. | User Fix |
| H.02.07 | Permanent Low Pressure | Pressure has been low for too long. Check for leaks on radiators and refill. | User Fix |
| E.01.04 | Flame Loss (5x in 24h) | Boiler lost flame repeatedly. Check gas supply. Reset boiler. If persistent, requires engineer. | Reset/Call |
| E.01.17 | No Water Circulation | Permanent circulation failure. Pump may be seized, or the system is full of sludge/blockage. | Engineer |
| E.04.10 | Ignition Failure | Burner failed to light after 4 attempts. Check gas supply and look for frozen condensate pipe in winter. | Reset/Call |
| E.00.04 | Return Temp Sensor Disconnected | Wiring issue or faulty NTC component. Boiler cannot monitor efficiency. | Engineer |
| E.04.01 | Flow Temp Sensor Short | Short circuit in the main temperature sensor. Boiler will shut down to prevent overheating. | Engineer |
| E.04.13 | Fan Impeller Blocked | Fan blockage or maximum RPM exceeded. Critical safety fault. | Engineer |
| A.00.34 | Outdoor Sensor Missing | Expected outdoor sensor not detected (only if weather compensation is fitted). | Engineer |
Classic Series: Platinum, Duo-tec, Main Eco
These robust models use the traditional "E" codes. If you have a Duo-tec, Platinum, or Main Eco Compact, use the table below. Note that E119 is the most common code owners will encounter.
| Error Code | Fault Description | Troubleshooting / Meaning | Action |
|---|---|---|---|
| E118 | Low Water Pressure (< 0.5 bar) | System pressure is critical. Repressurise via filling loop. | User Fix |
| E119 | Low Water Pressure | Older variant of E118. Requires topping up water to 1.5 bar. | User Fix |
| E133 | Ignition Failure / No Gas | Check gas supply. Ensure condensate pipe isn't frozen. Reset. | Reset/Call |
| E110 | Overheat Fault | Boiler too hot. Bleed radiators. Wait for cool down & reset. | User/Call |
| E160 | Fan Fault | Fan not running or speed signal lost. Fumes cannot be expelled. | Engineer |
| E168 | PCB / Unknown State | "Ghost" fault. Electrical supply issue or PCB memory corruption. | Engineer |
| E20 | Central Heating Sensor | NTC Sensor fault (Short or Open circuit). | Engineer |
| E50 | Hot Water Sensor | DHW NTC Sensor fault. Hot water may fluctuate or stop. | Engineer |
| E125 | Circulation Fault | Water not moving. Pump failure or air lock in the main exchanger. | Engineer |
In-Depth Troubleshooting & Fixes
Detailed steps for the most common issues we see in the field.
How to Fix Low Pressure (A.02.06 / E118 / E119)
Diagnosis: Your pressure gauge is reading below 1.0 bar (often close to zero). The boiler shuts down to protect the pump and heat exchanger from running dry.
The Fix:
- Turn off the boiler at the mains (optional but recommended).
- Locate the Filling Loop. On modern Baxi 600/800 models, this may be a clearly marked "Easy-Fill" link (a blue or green lever). On older models, it is a silver braided hose with one or two black taps underneath the boiler.
- Open the tap(s) slowly. You will hear water hissing as it enters the system.
- Keep an eye on the pressure gauge. When it rises to 1.5 bar (usually the green zone), close the tap(s) immediately.
- Reset the boiler. The error code should clear.
Note: If you have to do this every week, you have a leak in your system (check radiator valves or underfloor heating manifolds).
Ignition Failure (E.04.10 / E133 / E28)
Diagnosis: The boiler attempts to fire (you might hear clicking from the spark generator) but fails to establish a stable flame.
Common Causes:
- No Gas: Check if other gas appliances (hob/cooker) are working. If not, check your gas meter valve—it might have been bumped closed.
- Frozen Condensate (Winter): This is very common in cold snaps. The white plastic pipe running from your boiler to the outside drain may be blocked with ice, causing waste water to back up. Thaw the external pipe with warm (not boiling) water.
- Dirty Electrodes: If gas is present and the pipe is clear, the internal spark or sensing electrodes may be worn or carbonised. This requires an engineer to service the combustion chamber.
The "Ghost" Error (E168)
Diagnosis: The boiler displays E168 and stops working. This code essentially means "The PCB detected a fault but doesn't know what it is."
Context: This often happens after a power cut or a voltage spike in your home's electricity. It can also occur if the boiler was shut down incorrectly.
The Fix: Try a hard reset by turning the boiler off at the fused spur (wall switch) for 2 minutes, then turning it back on. If the error persists, the PCB (Printed Circuit Board) is likely damaged and needs replacing by a pro.
No Hot Water (Heating Works Fine)
Diagnosis: Your radiators are hot, but the water from the tap is stone cold. No error code is displayed.
Likely Cause: This is usually a Diverter Valve fault. The valve is stuck in the "heating" position and isn't switching over to heat the hot water plate exchanger when you open the tap.
Action: This is a mechanical failure. A boiler engineer will need to replace the diverter valve cartridge or the motor.
Radiators Cold at the Bottom (Sludge)
Diagnosis: Radiators are hot at the top but cold at the bottom. The boiler may be making kettling (banging) noises.
Cause: Magnetite (black iron oxide sludge) has settled in the bottom of your radiators, preventing hot water circulation.
The Fix: A chemical flush or a professional "Powerflush" is required. You should also have a Magnetic Filter (like a MagnaClean) installed to prevent future buildup. This improves boiler efficiency and longevity.
Frequently Asked Questions
How do I reset my Baxi boiler?
Most Baxi boilers have a dedicated reset button or a dial. Press and hold the reset button for approx. 3-5 seconds until the display clears or resets. On some Duo-tec models, you turn the selector knob to the 'R' position, hold for 5 seconds, and release.
How often should I service my Baxi boiler?
Manufacturers and Gas Safe recommend an annual service. This ensures the boiler is safe, running efficiently, and keeps your warranty valid. Missing a service can void your 7 or 10-year warranty.
Why is my boiler making a loud banging noise?
This is often called "kettling." It is caused by limescale or sludge build-up on the heat exchanger. The water is boiling into steam inside the block because it can't flow fast enough. It requires chemical descaling or a powerflush.
My boiler is leaking water, what should I do?
Turn the boiler off at the mains electricity and turn off the water supply to the boiler if possible. Do not attempt to fix a leak inside the casing. Call a professional immediately as water and electricity are a dangerous mix.
Can I install a smart thermostat (Nest or Hive) on my Baxi?
Yes, almost all modern Baxi boilers (including the 600, 800, Duo-tec, and Platinum ranges) are compatible with smart thermostats like Nest, Hive, and Tado. They can usually be wired directly into the boiler's OpenTherm or 230V switching connections.
My hot water fluctuates between hot and cold, why?
This is a classic sign of a blocked Plate Heat Exchanger. Sludge or limescale prevents the heat from transferring to your hot water effectively. The boiler overheats, shuts off to cool down, and then fires again, causing the "hot-cold-hot" cycle. An engineer can flush or replace the plate exchanger.
How long is the warranty on a Baxi boiler?
Baxi offers generous warranties ranging from 2 years (standard models) up to 10 years (Baxi 800 / Platinum series), provided the boiler is installed by a certified engineer and serviced annually. If you miss your annual service, the warranty may be void.
Cannot Resolve the Error?
If your code indicates a component failure (like Fan, PCB, or Sensor) or if basic troubleshooting fails, you need a certified expert. Don't risk your safety with DIY repairs on gas appliances.
Book a Baxi Engineer - 020 4616 5598Specialists in Baxi Combi, System, and Heat-Only boilers.
With many years on the tools in all aspects of the engineering industry has given me a second to none skill set which enables me to provide a leading professional service to my customers with a wealth of knowledge and highly skilled engineers to successfully cover all your plumbing, heating, AC and catering equipment requirements.
