Baxi EcoBlue Combi Fault codes & diagnostics

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

Combi Natural GasLPG 12-40 kW 2015 onwards Discontinued
GC Numbers 47-077-0847-077-0947-077-10
Download the Baxi EcoBlue Combi 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.
1 Emergency 22 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
47-077-08 Ecoblue + 24 Combi ErP 2015–present
47-077-09 Ecoblue + 28 Combi ErP 2015–present
47-077-10 Ecoblue + 33 Combi ErP 2015–present
Just want the most common Baxi EcoBlue Combi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 28 documented codes

Tap any card for details

LED / flash-pattern codes
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 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 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 to see if it clears the fault and restarts automatically
  2. If the fault persists and turns into a solid red light, try a manual reset
  3. Check that your gas pre-payment meter (if applicable) has credit

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
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 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 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
20

Your boiler has stopped working because it cannot accurately measure the temperature of the water being circulated to your radiators.

High Engineer only £120-220

Parts commonly replaced

  • Central Heating NTC sensor
  • Wiring harness

Related codes

Full explanation for 20
28

Your boiler has detected a problem with a temperature sensor inside the flue system, which stops the unit from operating to ensure it remains safe.

High Engineer only £120-220

Parts commonly replaced

  • Flue NTC Sensor
  • Wiring harness
  • PCB

Related codes

Full explanation for 28
40

Your boiler is struggling because a sensor that monitors the temperature of the water returning to the system is failing, which prevents it from heating your home correctly.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC thermistor sensor
  • Wiring harness

Related codes

Full explanation for 40
109

Your boiler has detected that water is not flowing through the system correctly, which is preventing it from heating your home safely.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve

Related codes

Full explanation for 109
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
111

Your boiler has automatically shut down because it has detected that its internal water temperature has become dangerously high.

High Engineer only £120-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Pump
  • Heat Exchanger

Related codes

Full explanation for 111
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 filling loop valves are fully closed
  2. Switch off the boiler and allow the system to cool
  3. Bleed water from a radiator using a bleed key to reduce pressure
  4. Monitor the pressure gauge until it returns to between 1.0 and 1.5 bar

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
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
Showing 21–28 of 28
130

Your boiler has detected that the temperature of the gases leaving your flue is too high, so it has shut itself down to prevent any damage.

High Engineer only £150-250

Parts commonly replaced

  • Flue NTC sensor
  • Wiring harness
  • PCB

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
151

Your boiler has failed to light the flame needed to heat your water and home, and has safely shut down to prevent gas from building up.

High Engineer only £120-250

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 151
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
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 is struggling to accurately measure the temperature of the water being heated for your taps and shower, so it has stopped producing hot water to prevent damage.

High Engineer only £120-220

Parts commonly replaced

  • Domestic Hot Water NTC Sensor

Related codes

Full explanation for 321
384

Your boiler has detected a flame signal when it should be turned off, so it has locked itself out to prevent a potential safety issue.

Emergency Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Gas Valve
  • Flame Rectification Probe
Full explanation for 384
E118

Your boiler has stopped working because the amount of water inside the system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the filling loop, which is a flexible silver hose connected to two valves under the boiler.
  2. Open the valves slowly to allow water into the system until the pressure gauge on the front reads between 1.0 and 1.5 bar.
  3. Close the valves firmly and check to ensure the boiler restarts.

Parts commonly replaced

  • Pressure relief valve
  • 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 Diagnostic Your boiler has detected that the water inside the heating system has become too hot and is shutting down to prevent damage. 02 Diagnostic Your boiler has lost communication with the weather sensor installed outside your home, meaning it cannot automatically adjust its temperature based on outdoor conditions. 03 Diagnostic Your boiler is struggling to accurately measure the temperature of the hot water it is attempting to provide. 04 Diagnostic Your boiler is having trouble sensing the temperature of your hot water, which prevents it from heating water properly for your taps. 05 Diagnostic Your boiler has detected that the water pressure inside the heating system is too low to operate safely. 06 Diagnostic Your boiler has detected that the water returning from your radiators is not at the expected temperature, causing it to stop heating to prevent internal damage. 07 Diagnostic Your boiler has detected that the flue gases are getting too hot, so it has safely shut itself down to prevent overheating. 10 Diagnostic Your boiler is struggling to accurately measure or circulate the hot water needed for your radiators. 12 Diagnostic Your boiler is failing to detect a flame, so it has safely shut itself down to prevent a gas build-up. 13 Diagnostic This code is simply an advisory reminder that your boiler has reached a pre-programmed number of operating hours and is due for its regular annual service. 14 Diagnostic Your boiler has detected a temperature issue in the central heating flow sensor, meaning it cannot accurately tell if your radiators are heating up properly. 15 Status Your boiler is signalling an issue with how it manages its secondary heating zone, which may prevent your home from warming up as expected. 16 Status Your boiler is struggling to correctly detect that you have turned on a hot water tap, meaning it isn't heating the water as it should. 17 Status Your boiler is currently running a background self-checking process or is in a temporary state of transition, so it should resolve itself automatically without any action on your part. 18 Status Your boiler is currently set to a special mode intended for systems connected to solar panels rather than standard household heating. 19 Diagnostic Your boiler has detected an internal communication error between its main control boards, which prevents it from operating correctly.