Baxi EcoBlue Heat Fault codes & diagnostics

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

Regular Natural Gas 12-30 kW 2015-present

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.
24 High 3 Medium 7 Low
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 34 documented codes

Tap any card for details

LED / flash-pattern codes
1 green flash

Your boiler has reached the correct temperature and is simply taking a natural rest; it is working exactly as it should.

Low DIY-safe

What to check first

  1. Check if your room thermostat is set to the desired temperature
  2. Wait for the boiler to restart automatically when the water temperature drops
  3. No further action is required as this is normal operation
Full explanation for 1 green flash
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 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
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
Showing 11–20 of 34
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
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
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
119

Your boiler has stopped working because the water pressure in the central heating system has dropped too low.

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/levers on the hose until you hear water flowing.
  3. Watch the pressure gauge and close the taps once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • Pressure sensor
  • Expansion vessel

Related codes

Full explanation for 119
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
127

Your boiler has failed to heat the hot water tank to a high enough temperature to kill off bacteria, which is a safety routine it performs periodically.

Medium DIY-safe £90-200

What to check first

  1. Check that your hot water cylinder thermostat is not turned down too low
  2. Ensure your hot water timer is set to allow the boiler enough time to complete a full heating cycle
  3. Reset the boiler to see if the cycle completes successfully on the next attempt

Parts commonly replaced

  • Cylinder thermostat
  • NTC water temperature sensor
  • Motorised zone valve

Related codes

Full explanation for 127
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
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
153

Your boiler has been manually reset too many times and has temporarily locked itself to prevent further issues.

High DIY-safe £0-120

What to check first

  1. Switch the boiler electrical supply off at the spur switch
  2. Wait for at least 30 seconds
  3. Switch the power back on to allow the system to clear the lockout

Parts commonly replaced

  • None (Software reset)
  • PCB (if error persists)

Related codes

Full explanation for 153
Showing 21–30 of 34
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
164

Your boiler has detected a problem with the sensor or switch that monitors water movement, preventing the system from heating up properly.

High Engineer only £120-240

Parts commonly replaced

  • Water pressure sensor
  • Flow switch
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 164
166

Your boiler has detected an issue with the way it is venting or drawing air, causing it to shut down for safety.

High Engineer only £120-220

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan
Full explanation for 166
270

Your boiler has detected that it is heating up too quickly without enough water circulating through it, causing it to shut down to prevent overheating.

High DIY-safe £100-£350

What to check first

  1. Check that your boiler pressure gauge is between 1.0 and 1.5 bar
  2. If the pressure is low, top up the system using the filling loop
  3. Ensure all radiator valves are open and bleed any trapped air from your radiators
  4. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Circulating Pump
  • Central Heating Return Filter
  • Overheat Thermostat
Full explanation for 270
432

Your boiler has detected an issue with its electrical grounding system, which is a safety feature that prevents electrical faults.

High Engineer only £90-250

Parts commonly replaced

  • Wiring harness
  • Printed Circuit Board (PCB)
  • Earth connection leads
Full explanation for 432
433

Your boiler has shut down because it has detected that it is getting far too hot, likely due to water not circulating properly through the system.

High DIY-safe £120-£350

What to check first

  1. Check that your radiator valves are fully open
  2. Ensure there is enough water pressure in the system (usually between 1 and 1.5 bar)
  3. Bleed your radiators to remove any trapped air
  4. Reset the boiler using the selector switch

Parts commonly replaced

  • Pump
  • Main Heat Exchanger
  • Temperature Sensor (NTC)
  • Diverter Valve

Related codes

Full explanation for 433
E10

Your boiler is having trouble reading the outside temperature, which may cause it to run less efficiently or at the wrong temperature.

Low Engineer only £90-180

Parts commonly replaced

  • Outdoor temperature sensor
  • External wiring/cabling
Full explanation for E10
E20

Your boiler is struggling to monitor the temperature of the water circulating through your radiators, causing the system to stop heating your home.

High Engineer only £90-160

Parts commonly replaced

  • Central heating NTC thermistor
  • Connecting wiring harness

Related codes

Full explanation for E20
E28

Your boiler has detected a problem with the sensor that monitors the temperature of the exhaust gases, and it has shut down as a safety precaution.

High Engineer only £120-190

Parts commonly replaced

  • Flue Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for E28
Showing 31–34 of 34
E54

The boiler is struggling to detect when you turn on a hot tap, which may result in lukewarm water or no hot water at all.

Medium Engineer only £120-210

Parts commonly replaced

  • DHW flow sensor
  • Flow turbine
  • Wiring harness

Related codes

Full explanation for E54
E78

Your boiler has lost its ability to accurately measure water pressure, which prevents it from running safely.

High Engineer only £140-£220

Parts commonly replaced

  • Water pressure sensor
  • Pressure switch wiring harness
Full explanation for E78
E100

Your boiler's internal computer has lost track of the time or date, which can prevent your heating schedules from working correctly.

Low DIY-safe £0-120

What to check first

  1. Locate the control panel on the front of the boiler
  2. Enter the settings menu to find the 'Time and Date' options
  3. Update the clock to the current time and save the settings

Parts commonly replaced

  • Printed Circuit Board (PCB)
Full explanation for E100
E109

Your boiler is struggling to move heated water through the system, causing it to shut down to prevent overheating.

High DIY-safe £100-£350

What to check first

  1. Check that the boiler pressure is between 1.0 and 1.5 bar on the gauge
  2. Ensure all radiator valves are fully open
  3. Bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Circulation pump
  • Main heat exchanger
  • System filter
Full explanation for E109