Baxi EcoBlue Heat Fault codes & diagnostics

48 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Regular Natural Gas 12-30 kW 2014-2015 Discontinued
GC Numbers 41-077-9541-077-9641-077-9741-077-9841-077-9941-470-0141-470-0241-470-0341-470-0441-470-0541-470-06
Download the Baxi EcoBlue Heat manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
43 High 1 Medium 4 Low
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-077-95 Ecoblue 12 System 2014–2015
41-077-96 Ecoblue 15 System 2014–2015
41-077-97 Ecoblue 18 System 2014–2015
41-077-98 Ecoblue 24 System 2014–2015
41-077-99 Ecoblue 28 System 2014–2015
41-470-01 Ecoblue 32 System 2014–2015
41-470-02 EcoBlue Heat 12 2014–2015
Just want the most common Baxi EcoBlue Heat faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 48 documented codes

Tap any card for details

LED / flash-pattern codes
1 flash green

Your boiler has shut down because it is getting too hot too quickly, usually because the water inside isn't circulating properly.

High DIY-safe £100-£350

What to check first

  1. Check that your pump is running and hasn't seized
  2. Ensure all radiator valves are fully open to allow water to flow
  3. Check that the boiler pressure is between 1.0 and 1.5 bar
  4. Bleed all radiators to remove trapped air pockets

Parts commonly replaced

  • Circulation Pump
  • Flow/Return Thermistor
  • Heat Exchanger (De-scaling)

Related codes

Full explanation for 1 flash green
1 flash red

Your boiler has detected that water is either not moving through the system correctly or a temperature sensor has failed, preventing it from heating up safely.

High DIY-safe £75-180

What to check first

  1. Check that your central heating valves (under the boiler) are fully open
  2. Ensure all radiator valves are turned on to allow water to flow
  3. Reset the boiler by turning the selector switch to the 'R' position for five seconds

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Return temperature sensor (NTC)
  • Circulation pump

Related codes

Full explanation for 1 flash red
1 red flash

Your boiler has detected that it is getting too hot or that water isn't moving through the system correctly, causing it to shut down for safety.

High DIY-safe £120-250

What to check first

  1. Check that your radiator valves are open
  2. Ensure your system water pressure is between 1 and 1.5 bar on the gauge
  3. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Temperature Sensor (NTC Thermistor)
  • Circulating Pump
  • Overheat Thermostat

Related codes

Full explanation for 1 red flash
2 flashes green

Your boiler has shut down because a safety circuit or external control link has been disconnected or broken.

High Engineer only £90-180

Parts commonly replaced

  • User Interaction Controller
  • Wiring Harness
  • External Controls Link

Related codes

Full explanation for 2 flashes green
2 flashes red

Your boiler has got too hot and has shut itself down as a safety precaution.

High DIY-safe £120-350

What to check first

  1. Check that your radiator valves are open
  2. Ensure your system water pressure is between 1 and 1.5 bar
  3. Turn the selector switch to 'Reset' for five seconds and then back to 'On'

Parts commonly replaced

  • Over-temperature Thermostat
  • Circulation Pump
  • PCB

Related codes

Full explanation for 2 flashes red
2 red flashes

Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.

High DIY-safe £100-£350

What to check first

  1. Check that your radiator valves are open and not turned to zero.
  2. Ensure your system water pressure is between 1 and 1.5 bar on the gauge.
  3. Turn the selector switch to the reset position for five seconds and then back to 'onn'.

Parts commonly replaced

  • Overheat Thermostat
  • Circulating Pump
  • Main Heat Exchanger (Flushing)

Related codes

Full explanation for 2 red flashes
3 flashes green

Your boiler was working but the flame has unexpectedly gone out, causing the system to stop for safety.

High DIY-safe £100-£280

What to check first

  1. Check if other gas appliances in your home, like a hob, are still working to ensure gas supply.
  2. Verify that your prepaid gas meter has credit if applicable.
  3. Restart the boiler by turning the selector switch to the reset position for five seconds.

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Spark generator

Related codes

Full explanation for 3 flashes green
3 flashes red

Your boiler is failing to light the gas or cannot stay lit, which means your heating and hot water have stopped working.

High DIY-safe £100-350

What to check first

  1. Check if other gas appliances, like a cooker, are working to confirm gas supply is active
  2. Check that your credit meter has not run out of funds
  3. Press and hold the reset button for five seconds

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 3 flashes red
3 green flashes

Your boiler has briefly lost its flame and is trying to restart itself, which is often a temporary glitch that might resolve without any action.

Low DIY-safe £100-250

What to check first

  1. Monitor the boiler for several minutes to see if the flame re-establishes automatically.
  2. Perform a manual reset by turning the selector knob to 'R' for five seconds if the boiler does not self-correct.
  3. Check that your gas supply is active by testing another gas appliance like a hob.

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve

Related codes

Full explanation for 3 green flashes
3 red flashes

Your boiler has tried to light itself several times but cannot establish a flame, meaning you will have no heating or hot water until it is reset or repaired.

High DIY-safe £120-280

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to ensure gas is reaching the property
  2. Check that your gas meter has credit if you use a pre-payment system
  3. Press and hold the reset button for five seconds to see if the boiler restarts

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Lead
  • Printed Circuit Board (PCB)
Full explanation for 3 red flashes
Showing 11–20 of 48
4 flashes green

Your boiler is having trouble sending messages between its internal electronic brains, meaning it cannot start the heating or hot water until the connection is restored.

High Engineer only £120-450

Parts commonly replaced

  • Wiring harness
  • Printed Circuit Board (PCB)
  • User interface/Display panel

Related codes

Full explanation for 4 flashes green
4 flashes red

Your boiler's fan, which safely clears exhaust gases, is either not spinning at the correct speed or has failed to start.

High Engineer only £220-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Venturi tube

Related codes

Full explanation for 4 flashes red
4 green flashes

Your boiler is having a temporary 'handshake' issue between its internal electronic brains, but it should fix itself automatically.

Low DIY-safe £0-120

What to check first

  1. Wait for the boiler to self-reset as this is often a temporary glitch
  2. If the flashing continues, turn the selector switch to 'Reset' for five seconds
  3. Monitor the boiler to see if the green flashes return

Parts commonly replaced

  • None (usually self-correcting)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 4 green flashes
4 red flashes

Your boiler's fan is not spinning or communicating correctly with the system, preventing the boiler from starting safely.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 4 red flashes
5 flashes green

Your boiler's computer brain has become confused by its internal settings or has suffered a hardware failure, preventing it from starting up.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Parameter Key
Full explanation for 5 flashes green
5 flashes red

Your boiler's internal computer has lost communication with its main control board, meaning it cannot process the instructions needed to run properly.

High Engineer only £180-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for 5 flashes red
5 green flashes

Your boiler has experienced a brief digital hiccup or settings error and is attempting to fix itself automatically.

Low DIY-safe £0-350

What to check first

  1. Wait for the boiler to complete its automatic self-reset process
  2. Monitor the display to see if the flashing stops naturally
  3. If the flashing continues for more than 10 minutes, try turning the boiler off and back on at the fused spur switch

Parts commonly replaced

  • None (Software reset)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 5 green flashes
5 red flashes

Your boiler's internal memory chip has developed a communication fault, meaning the control board can no longer read its essential settings.

High Engineer only £120-250

Parts commonly replaced

  • Parameter Storage Unit (PSU)
  • Printed Circuit Board (PCB)
Full explanation for 5 red flashes
6 flashes green

Your boiler's electronic brain has encountered an internal error and is unable to manage the heating process safely.

High Engineer only £250-£450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Combustion Control Unit

Related codes

Full explanation for 6 flashes green
6 flashes red

Your boiler has stopped working because its internal computer is struggling to talk to the connected parts or there is an error in its settings.

High Engineer only £120-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Harness
  • External Controls Interface

Related codes

Full explanation for 6 flashes red
Showing 21–30 of 48
6 green flashes

Your boiler has encountered a minor glitch and is attempting to restart itself automatically without you needing to do anything.

Low DIY-safe £0-120

What to check first

  1. Wait up to 15 minutes for the boiler to complete its self-reset process
  2. Ensure the boiler's electrical supply is stable and not fluctuating
  3. Turn the selector switch to 'Reset' and back to 'On' if the light continues to flash

Parts commonly replaced

  • No parts usually required
  • Control PCB
Full explanation for 6 green flashes
6 red flashes

Your boiler has detected an internal communication or unexpected component fault and has stopped working as a safety precaution.

High DIY-safe £100-£350

What to check first

  1. Turn the selector switch to the 'Reset' position and hold for 5 seconds.
  2. Release the switch and wait for the boiler to attempt to restart.
  3. Ensure your gas supply is active and your credit meter (if applicable) has funds.

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
  • Gas Valve
Full explanation for 6 red flashes
Digital codes
08

Your boiler has detected an internal communication error and needs to be reset.

High DIY-safe £0-120

What to check first

  1. Locate the selector switch on the front of the boiler
  2. Turn the switch to the 'R' (Reset) position and hold for at least 5 seconds
  3. Release the switch and wait for the boiler to attempt to restart

Parts commonly replaced

  • None (Logic Reset)
  • Main PCB

Related codes

Full explanation for 08
20

Your boiler's temperature sensor is providing an incorrect reading, which has caused the system to stop heating your home as a safety precaution.

High Engineer only £120-200

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring harness

Related codes

Full explanation for 20
28

Your boiler has detected a problem with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.

High Engineer only £120-220

Parts commonly replaced

  • Flue NTC Thermistor
  • Wiring harness
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 28
40

Your boiler has detected a problem with the sensor that monitors the temperature of the water returning from your radiators.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating Return NTC Thermistor
  • Wiring harness connector

Related codes

Full explanation for 40
109

Your boiler is struggling to move water around your heating system effectively, which is causing it to stop for safety reasons to prevent overheating.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve

Related codes

Full explanation for 109
109 R

Your boiler has likely detected that water is not moving around the system properly, causing it to overheat and shut down for safety.

High DIY-safe £180-450

What to check first

  1. Check that your radiator valves are open
  2. Ensure the boiler pressure is between 1 and 1.5 bar
  3. Check for any frozen or blocked external pipes
  4. Reset the boiler to see if the fault clears

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger (Flushing)
  • Flow/Return Temperature Sensors

Related codes

Full explanation for 109 R
110

Your boiler has switched itself off because it has reached too high a temperature, likely due to trapped air or a blockage stopping water from circulating.

High DIY-safe £100-250

What to check first

  1. Turn off the boiler and allow it to cool down completely.
  2. Use a radiator key to bleed all radiators to remove any trapped air.
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it has dropped.
  4. Turn the boiler back on and press the 'Reset' button.

Parts commonly replaced

  • Overheat Thermostat
  • Circulating Pump
  • NTC Temperature Sensor
Full explanation for 110
110 R

Your boiler has shut itself down because it has overheated, likely because the water isn't being circulated around the system properly.

High DIY-safe £180-350

What to check first

  1. Ensure all radiator valves are fully open
  2. Check that your system water pressure is between 1 and 1.5 bar
  3. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Main Heat Exchanger (Cleaning/Flushing)

Related codes

Full explanation for 110 R
Showing 31–40 of 48
111

Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage.

High Engineer only £150-£300

Parts commonly replaced

  • Pump
  • System filter
  • Heat exchanger
  • Safety thermostat

Related codes

Full explanation for 111
111 R

Your boiler has shut down because it has detected it is getting too hot, similar to a safety trip switch on an electrical appliance.

High DIY-safe £100-280

What to check first

  1. Check that your radiator valves are open to allow water to flow
  2. Ensure your system pressure is topped up to between 1 and 1.5 bar
  3. Press the Reset button for five seconds and wait for the boiler to restart

Parts commonly replaced

  • Overheat Thermostat
  • Water Pump
  • Thermistor (NTC Sensor)

Related codes

Full explanation for 111 R
117

Your boiler has too much water in the system, which puts extra stress on the internal parts and may cause it to shut down for safety.

Medium DIY-safe £80-160

What to check first

  1. Check that the external filling loop valves are tightly closed.
  2. Bleed water from a radiator using a radiator key to reduce the system pressure.
  3. Monitor the pressure gauge until it returns to the normal range (typically 1.0 to 1.5 bar).
  4. Press the reset button if the boiler does not restart automatically.

Parts commonly replaced

  • Filling loop valve
  • Pressure Relief Valve (PRV)
  • Expansion vessel

Related codes

Full explanation for 117
118

Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath your boiler.
  2. Slowly open the one or two taps/valves on the filling loop until you hear water entering the system.
  3. Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.

Parts commonly replaced

  • Filling loop valves
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 118
125

Your boiler has detected that water isn't moving through the system properly, which is causing it to overheat and shut down for safety.

High DIY-safe £150-£350

What to check first

  1. Check that your system pressure is between 1 and 1.5 bar on the pressure gauge
  2. Ensure all radiator valves and isolation valves under the boiler are fully open
  3. Bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Circulating Pump
  • Pump Lead
  • Main Heat Exchanger

Related codes

Full explanation for 125
125 R

Your boiler has detected that water is not circulating correctly through the system, causing it to shut down to prevent overheating.

High DIY-safe £180-£350

What to check first

  1. Check that your radiator valves and isolation valves under the boiler are fully open.
  2. Ensure all radiators are bled to remove trapped air from the system.
  3. Confirm that your system pressure is topped up to between 1 and 1.5 bar.

Parts commonly replaced

  • Circulation pump
  • Pump head
  • Primary heat exchanger (flushing service)

Related codes

Full explanation for 125 R
128

Your boiler started to heat up but the flame went out unexpectedly while it was running.

High DIY-safe £100-£350

What to check first

  1. Check that your gas pre-pay meter has credit
  2. Ensure other gas appliances in your home are working to confirm gas supply
  3. Press the 'Reset' button for five seconds

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve

Related codes

Full explanation for 128
130

Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent internal damage.

High Engineer only £120-£250

Parts commonly replaced

  • Flue NTC Sensor
  • Heat Exchanger (cleaning or replacement)
  • Burner Insulation Panel

Related codes

Full explanation for 130
133

Your boiler has tried to ignite but failed to stay alight, which is often caused by a lack of gas supply or a blocked condensation pipe.

High DIY-safe £100-£350

What to check first

  1. Check that your gas supply is turned on and you have credit on your meter.
  2. During freezing weather, check if your external white plastic condensate pipe is frozen and thaw it with warm water.
  3. Press the Reset button for five seconds.

Parts commonly replaced

  • Gas Valve
  • Ignition Electrode
  • Printed Circuit Board (PCB)
Full explanation for 133
133 R

Your boiler has tried to light several times but has been unable to establish a flame, often because gas isn't reaching the burner or the ignition sparks aren't working.

High DIY-safe £120-350

What to check first

  1. Check that your gas meter has credit and the isolation valve is open
  2. Check if other gas appliances in your home, like a hob, are working correctly
  3. Press and hold the 'R' or Reset button for five seconds to attempt a restart

Parts commonly replaced

  • Flame Sensing Electrode
  • Ignition Lead
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 133 R
Showing 41–48 of 48
151

Your boiler has attempted to light the gas flame but failed, meaning your heating and hot water will not work until the fault is corrected.

High Engineer only £150-300

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 151
151 R

Your boiler is failing to light the flame or keep it burning, which means your heating and hot water have stopped working.

High DIY-safe £80-280

What to check first

  1. Check that your gas supply is turned on and other gas appliances like your hob are working
  2. Reset the boiler by turning the selector switch to 'R' and holding for at least five seconds
  3. Ensure the condensate pipe (the white plastic pipe outside) hasn't frozen in cold weather

Parts commonly replaced

  • Ignition electrode
  • Flame sensing probe
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 151 R
160

Your boiler's fan is not spinning at the correct speed, which prevents the system from safely clearing exhaust fumes and starting the ignition process.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 160
160 R

Your boiler has detected an issue with the fan that safely clears away exhaust fumes, causing the system to shut down for safety.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Fan wiring harness
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 160 R
162

Your boiler has detected an issue with how it clears exhaust gases or brings in fresh air, preventing it from firing up for safety.

High Engineer only £120-£250

Parts commonly replaced

  • Air Pressure Switch
  • Venturi tube
  • Fan
Full explanation for 162
321

Your boiler has detected an issue with a temperature sensor, most likely on the hot water circuit, preventing it from heating up correctly.

High Engineer only £90-160

Parts commonly replaced

  • DHW NTC thermistor
  • Wiring harness

Related codes

Full explanation for 321
384

Your boiler thinks it sees a flame even though it hasn't tried to light one yet, which stops it from starting up for safety reasons.

High Engineer only £120-300

Parts commonly replaced

  • Ionisation probe
  • Flame sensing electrode
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 384
E118

Your boiler has detected that the water pressure in the central heating system is too low to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop, which is usually a flexible silver hose under the boiler.
  2. Slowly open both small valves on the filling loop until you hear water entering the system.
  3. Watch the pressure gauge on the boiler until it reaches between 1.0 and 1.5 bar, then close both valves tightly.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor
Full explanation for E118
Status & diagnostic codes

17 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

1 green flash Status Your boiler has reached the correct temperature and is simply taking a natural rest; it is working exactly as it should. 01 Status Your boiler has stopped working because it has detected an excessively high temperature, triggering a safety shutdown to prevent damage. 02 Diagnostic Your boiler has lost its connection to the outside temperature sensor, which helps the system run more efficiently based on the weather. 03 Diagnostic Your boiler has detected a problem with the sensor that monitors the temperature of your hot water, meaning it might struggle to heat your taps correctly. 04 Diagnostic Your boiler is having trouble measuring the temperature of your hot water because the sensor has likely developed a fault. 05 Diagnostic Your boiler has detected that the water pressure in the central heating system is too low for it to operate safely. 06 Diagnostic Your boiler has sensed a problem with the temperature sensor that monitors the water returning from your radiators. 07 Diagnostic Your boiler has shut down because it detected that the exhaust gases are becoming too hot, which is a safety feature to prevent damage or dangerous operation. 10 Diagnostic Your boiler has detected an issue with a temperature sensor that monitors the water going to your radiators, which may stop the heating from working correctly. 12 Diagnostic Your boiler has failed to detect a flame after several attempts and has locked out for safety. 13 Diagnostic Your boiler is simply displaying how many hours the burner has been running as part of a routine status update, rather than indicating a fault. 14 Diagnostic Your boiler is signalling that there is a fault with the primary zone's flow or return sensors, likely causing your central heating to stop working correctly. 15 Diagnostic Your boiler is signalling a demand for heating in a secondary heating zone, which is often just an informative status rather than a hardware failure. 16 Diagnostic Your boiler has detected a fault with the sensor that monitors the temperature of your hot water. 17 Diagnostic Your boiler is operating in a temporary de-aeration mode to remove air bubbles from the system and is not actually reporting a fault. 18 Diagnostic Your boiler has switched into a special solar heating mode, which is usually a settings error rather than a mechanical breakdown. 19 Diagnostic Your boiler is undergoing a routine start-up sequence where it displays the manufacturer's identification information.