BoilerFaultCodes 1 green flash
Your boiler has reached the required temperature and is naturally pausing its heating cycle; everything is working exactly as it should.
Baxi EP Fault codes & diagnostics
129 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Natural Gas 1990-2005 Discontinued
Replaced by: EP2000
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. 2 Emergency
109 High
10 Medium
8 Low
Just want the most common Baxi EP faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 129 documented codes
Tap any card for details
LED / flash-pattern codes
1 red flash Your boiler has sensed that it is getting too hot too quickly or that water isn't moving through the system properly.
Your boiler has sensed that it is getting too hot too quickly or that water isn't moving through the system properly.
What to check first
- Check that your radiator valves are open
- Ensure the system pressure is between 1 and 1.5 bar
- Reset the boiler by turning the selector switch to 'R' for five seconds
Parts commonly replaced
- Temperature Sensor (NTC Thermistor)
- Circulation Pump
- Overheat Thermostat
Related codes
2 red flashes Your boiler has become too hot and has automatically shut itself down as a safety precaution.
Your boiler has become too hot and has automatically shut itself down as a safety precaution.
What to check first
- Ensure all radiator valves are fully open to allow water to circulate
- Check that your system pressure is between 1 and 1.5 bar on the gauge
- Allow the boiler to cool down, then move the selector switch to 'R' to reset
Parts commonly replaced
- Circulating Pump
- Overheat Thermostat
- Thermistor (NTC Sensor)
Related codes
3 green flashes Your boiler has temporarily lost its flame and is currently trying to restart itself automatically.
Your boiler has temporarily lost its flame and is currently trying to restart itself automatically.
What to check first
- Wait for the boiler to complete its automatic self-reset sequence
- Check that other gas appliances in the home are working correctly
- Ensure the external condensate pipe has not frozen if the weather is cold
- Monitor the control panel to see if the fault clears or turns into a solid red light
Parts commonly replaced
- Flame sensing electrode
- Gas valve
- Ignition lead
Related codes
3 red flashes Your boiler has tried to light itself several times without success, so it has shut down as a safety precaution.
Your boiler has tried to light itself several times without success, so it has shut down as a safety precaution.
What to check first
- Check that your gas supply is turned on at the meter
- If you have a prepaid meter, ensure you have sufficient credit
- Turn the selector switch to the reset position for five seconds, then back to the on position
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Flame Sensing Lead
Related codes
4 green flashes Your boiler is having a temporary 'conversation' issue between its internal computer parts and will usually fix itself shortly.
Your boiler is having a temporary 'conversation' issue between its internal computer parts and will usually fix itself shortly.
What to check first
- Wait for the boiler to self-reset as this is often a temporary glitch
- Turn the power to the boiler off and back on at the fused spur switch
- Monitor the lights to see if the flashing sequence changes or stops
Parts commonly replaced
- Printed Circuit Board (PCB)
- External Controller
Related codes
4 red flashes Your boiler's internal fan is not spinning correctly, which means the system cannot safely clear waste gases and will not ignite.
Your boiler's internal fan is not spinning correctly, which means the system cannot safely clear waste gases and will not ignite.
Parts commonly replaced
- Fan assembly
- Air pressure switch
- Main PCB
Related codes
5 green flashes Your boiler's internal computer has encountered a temporary settings glitch and is currently trying to fix itself.
Your boiler's internal computer has encountered a temporary settings glitch and is currently trying to fix itself.
What to check first
- Wait for the boiler to automatically reset itself
- Turn the power to the boiler off and back on at the fused spur switch
- If the flashing continues for more than 30 minutes, contact a Gas Safe engineer
Parts commonly replaced
- Printed Circuit Board (PCB)
Related codes
5 red flashes Your boiler's internal memory chip has developed a communication fault or become corrupted, preventing the system from starting up.
Your boiler's internal memory chip has developed a communication fault or become corrupted, preventing the system from starting up.
Parts commonly replaced
- Parameter Storage Unit (PSU)
- Main Control Board (PCB)
Related codes
6 green flashes Your boiler has experienced a small glitch and is trying to clear the problem on its own without you needing to do anything.
Your boiler has experienced a small glitch and is trying to clear the problem on its own without you needing to do anything.
What to check first
- Wait for the boiler to complete its self-reset cycle
- Monitor the lights to see if they return to a solid green status
- If the flashing persists for more than 30 minutes, try turning the power switch off and back on once
Parts commonly replaced
- None (Software reset)
- PCB (if fault becomes permanent)
Related codes
Showing 11–20 of 129
6 red flashes Your boiler has encountered a general electrical or communication error and needs to be reset to try and clear the fault.
Your boiler has encountered a general electrical or communication error and needs to be reset to try and clear the fault.
What to check first
- Locate the selector switch on the front of the boiler.
- Turn the switch to the 'Reset' position and hold it for five seconds.
- Return the switch to the original 'On' position and wait to see if the green light remains steady.
Parts commonly replaced
- Printed Circuit Board (PCB)
- External wiring harness
Related codes
FLASH FLASH ON Your boiler has detected an issue with the fan that safely pushes waste gases out of your home, causing the system to shut down for safety.
Your boiler has detected an issue with the fan that safely pushes waste gases out of your home, causing the system to shut down for safety.
Parts commonly replaced
- Fan assembly
- Air pressure switch
- PCB (Printed Circuit Board)
Related codes
FLASH OFF FLASH Your boiler is not receiving enough electrical power from the mains supply to operate safely.
Your boiler is not receiving enough electrical power from the mains supply to operate safely.
Parts commonly replaced
- PCB (Printed Circuit Board)
- External Voltage Stabilizer
Related codes
FLASH OFF ON Your boiler has shut down because it has detected it is getting too hot, which is a safety mechanism to prevent damage.
Your boiler has shut down because it has detected it is getting too hot, which is a safety mechanism to prevent damage.
What to check first
- Check that all radiator valves are fully open to allow water to circulate.
- Ensure there is enough water pressure in the system by checking the pressure gauge.
- Wait 30 minutes for the unit to cool down and then turn the selector switch to the reset position.
Parts commonly replaced
- Circulating Pump
- Overheat Thermostat
- Heat Exchanger (Cleaning/Descaling)
Related codes
FLASH ON FLASH Your boiler’s internal computer has encountered a critical error and can no longer communicate with the rest of the system.
Your boiler’s internal computer has encountered a critical error and can no longer communicate with the rest of the system.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
Related codes
FLASH ON ON Your boiler's internal computer has developed a fault and is unable to control the system correctly.
Your boiler's internal computer has developed a fault and is unable to control the system correctly.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
Related codes
ON FLASH FLASH Your boiler is struggling to move water around the system or has detected it is heating up too quickly without enough water inside.
Your boiler is struggling to move water around the system or has detected it is heating up too quickly without enough water inside.
What to check first
- Check your boiler pressure gauge and top it up to 1.5 bar if it is too low
- Ensure all radiator valves and isolation valves under the boiler are fully open
- Bleed your radiators to remove any trapped air that might be blocking water flow
Parts commonly replaced
- Circulation pump
- Main heat exchanger
- Pressure sensor
Related codes
ON FLASH ON Your boiler has detected a problem with its internal temperature sensors, which means it cannot accurately monitor the water temperature and has stopped working for safety.
Your boiler has detected a problem with its internal temperature sensors, which means it cannot accurately monitor the water temperature and has stopped working for safety.
Parts commonly replaced
- NTC Thermistor
- Wiring Harness
Related codes
ON OFF FLASH Your boiler has detected an electrical wiring issue where the power supply wires are connected the wrong way round.
Your boiler has detected an electrical wiring issue where the power supply wires are connected the wrong way round.
Parts commonly replaced
- External wiring connections
- Printed Circuit Board (PCB)
Related codes
ON ON FLASH Your boiler's internal computer has encountered a critical error and can no longer control the heating system safely.
Your boiler's internal computer has encountered a critical error and can no longer control the heating system safely.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Wiring Harness
Related codes
Digital codes
110 Your boiler has switched itself off because it has gotten too hot, likely due to trapped air or a blockage stopping water from flowing correctly.
Your boiler has switched itself off because it has gotten too hot, likely due to trapped air or a blockage stopping water from flowing correctly.
What to check first
- Turn off the boiler and wait for it to cool down.
- Bleed all radiators using a radiator key to remove trapped air.
- Check the boiler pressure gauge and top it up to 1.5 bar if it has dropped.
- Restart the boiler to see if the fault clears.
Parts commonly replaced
- Overheat Thermostat
- Circulation Pump
- NTC Sensor
Related codes
117 Your boiler has detected that there is too much water pressure in the system, which can cause internal leaks or damage if not reduced.
Your boiler has detected that there is too much water pressure in the system, which can cause internal leaks or damage if not reduced.
What to check first
- Check that the filling loop valves are fully closed
- Bleed water from a radiator using a bleed key to reduce pressure
- Monitor the pressure gauge to ensure it returns to between 1 and 1.5 bar
- Reset the boiler once the pressure is at the correct level
Parts commonly replaced
- Filling loop
- Expansion vessel
- Pressure relief valve
Related codes
118 Your boiler has stopped working because there is not enough water pressure in the system to operate safely.
Your boiler has stopped working because there is not enough water pressure in the system to operate safely.
What to check first
- Locate the filling loop, which is usually a flexible silver hose underneath the boiler.
- Slowly open the tap or taps on the filling loop to allow water into the system.
- Watch the pressure gauge and close the taps once the needle reaches between 1.0 and 1.5 bar.
Parts commonly replaced
- Filling loop
- Expansion vessel
- Pressure sensor
Related codes
119 Your boiler has stopped working because the water pressure in the system has dropped below the level needed to safely run your heating.
Your boiler has stopped working because the water pressure in the system has dropped below the level needed to safely run your heating.
What to check first
- Locate the filling loop, which is usually a flexible silver hose under the boiler.
- Slowly open the one or two taps/levers on the filling loop to let water into the system.
- Watch the pressure gauge and close the taps once the needle reaches between 1 and 1.5 bar.
Parts commonly replaced
- Filling loop
- Pressure sensor
- Expansion vessel
Related codes
125 Your boiler has stopped working because water is not flowing through the system correctly, which is causing it to overheat and shut down for safety.
Your boiler has stopped working because water is not flowing through the system correctly, which is causing it to overheat and shut down for safety.
What to check first
- Ensure all radiator valves (TRVs) are fully open
- Check that the boiler pressure is between 1 and 1.5 bar on the gauge
- Gently bleed air from your radiators using a radiator key
Parts commonly replaced
- Circulation Pump
- Water Pressure Sensor
- Main Heat Exchanger (if blocked)
Related codes
127 Your boiler has failed to heat the hot water tank to a high enough temperature to kill off any potential bacteria.
Your boiler has failed to heat the hot water tank to a high enough temperature to kill off any potential bacteria.
What to check first
- Check that your hot water timer or programmer is set to be 'On' for at least an hour
- Ensure the hot water temperature dial on the boiler is turned up to its normal setting
- Reset the boiler to see if the cycle completes on the next attempt
Parts commonly replaced
- Cylinder NTC sensor
- Immersion heater
- External programmer
128 Your boiler started to heat up but the flame went out unexpectedly while it was running.
Your boiler started to heat up but the flame went out unexpectedly while it was running.
Parts commonly replaced
- Flame sensing electrode
- Ignition lead
- Gas valve
- Condensate trap
Related codes
133 Your boiler has failed to light the gas burner properly, meaning the system has locked out to keep you safe.
Your boiler has failed to light the gas burner properly, meaning the system has locked out to keep you safe.
What to check first
- Check if your prepaid gas meter has run out of credit
- Ensure your external gas emergency control valve is in the 'on' position
- Press and hold the Reset button for five seconds to see if the boiler restarts
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Spark Generator
Related codes
153 Your boiler has gone into a safety lockout mode and requires a manual reset to restart the ignition sequence.
Your boiler has gone into a safety lockout mode and requires a manual reset to restart the ignition sequence.
What to check first
- Locate the reset button or selector switch on the front control panel.
- Press and hold the reset button for at least 5 seconds.
- Wait for the boiler to attempt to reignite; if the code clears, monitor for recurrence.
Parts commonly replaced
- None (Reset required)
- Ignition Electrode
- PCB (if fault persists)
Related codes
160 Your boiler's fan is not running at the correct speed to safely clear waste gases, so the system has shut down for your safety.
Your boiler's fan is not running at the correct speed to safely clear waste gases, so the system has shut down for your safety.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
Showing 31–40 of 129
162 Your boiler is having trouble clearing away exhaust gases or drawing in fresh air, which prevents it from firing up safely.
Your boiler is having trouble clearing away exhaust gases or drawing in fresh air, which prevents it from firing up safely.
Parts commonly replaced
- Air Pressure Switch
- Venturi Tube
- Fan
Related codes
164 Your boiler has detected a problem reading the water pressure or flow, causing it to shut down for safety.
Your boiler has detected a problem reading the water pressure or flow, causing it to shut down for safety.
What to check first
- Check the pressure gauge on the front of the boiler is between 1 and 1.5 bar
- If the pressure is too low, use the filling loop to top it up
- Restart the boiler once the correct pressure is reached
Parts commonly replaced
- Water pressure sensor
- Flow switch
- Wiring harness
Related codes
166 Your boiler has detected an issue with how air is moving through the system, preventing it from lighting safely.
Your boiler has detected an issue with how air is moving through the system, preventing it from lighting safely.
Parts commonly replaced
- Air Pressure Switch
- Venturi Tube
- Fan
Related codes
270 Your boiler has detected that it is overheating because there is not enough water circulating through the system or there is an air pocket trapped inside.
Your boiler has detected that it is overheating because there is not enough water circulating through the system or there is an air pocket trapped inside.
What to check first
- Check the pressure gauge and top up the system to 1.5 bar if it is low
- Bleed all radiators to remove trapped air from the system
- Ensure all radiator valves and isolation valves under the boiler are fully open
- Reset the boiler to see if the fault clears
Parts commonly replaced
- Circulation Pump
- Automatic Air Vent
- Overheat Thermostat
Related codes
432 Your boiler has detected an electrical grounding issue which is preventing it from running safely.
Your boiler has detected an electrical grounding issue which is preventing it from running safely.
Parts commonly replaced
- Earth wiring loom
- Printed Circuit Board (PCB)
Related codes
433 Your boiler has shut down because its internal temperature has become too high, often caused by a lack of water flow through the system.
Your boiler has shut down because its internal temperature has become too high, often caused by a lack of water flow through the system.
What to check first
- Check that your home heating system pressure is between 1.0 and 1.5 bar
- Ensure all radiator valves and internal isolation valves are fully open
- Bleed all radiators to remove trapped air that might be blocking water flow
Parts commonly replaced
- Circulating Pump
- Heat Exchanger
- Temperature Sensors (NTC)
Related codes
E.00 – .04 Your boiler has stopped working because it cannot correctly measure the temperature of the water returning to the unit due to a faulty sensor or loose wiring.
Your boiler has stopped working because it cannot correctly measure the temperature of the water returning to the unit due to a faulty sensor or loose wiring.
Parts commonly replaced
- Return temperature sensor (NTC thermistor)
- Wiring harness connector
E.00 – .05 Your boiler has lost connection to the internal sensor that monitors water returning to the unit, preventing it from heating your home safely.
Your boiler has lost connection to the internal sensor that monitors water returning to the unit, preventing it from heating your home safely.
Parts commonly replaced
- Return temperature sensor (NTC thermistor)
- Wiring harness
- Control board (PCB)
E.01 – .02 Your boiler has stopped working because the temperature readings are the wrong way around, suggesting water is flowing incorrectly or a sensor is faulty.
Your boiler has stopped working because the temperature readings are the wrong way around, suggesting water is flowing incorrectly or a sensor is faulty.
Parts commonly replaced
- Flow/Return thermistor sensors
- Water pump
- Main PCB
E.01 – .04 Your boiler is struggling to keep its flame lit and has shut itself down as a safety precaution after failing to stay alight several times.
Your boiler is struggling to keep its flame lit and has shut itself down as a safety precaution after failing to stay alight several times.
What to check first
- Check that your gas emergency control valve is open and you have credit on your gas meter
- Check if other gas appliances in your home, such as a hob, are working correctly
- Perform a reset by turning the selector switch to the 'R' position for at least five seconds
Parts commonly replaced
- Flame sensing electrode
- Gas valve
- Spark generator
Related codes
Showing 41–50 of 129
E.01 – .11 Your boiler's fan is not spinning at the correct speed to safely clear exhaust fumes, often due to a strong gust of wind or a mechanical failure.
Your boiler's fan is not spinning at the correct speed to safely clear exhaust fumes, often due to a strong gust of wind or a mechanical failure.
Parts commonly replaced
- Fan assembly
- Air pressure switch
- Gas/Air unit
E.01 – .12 Your boiler has detected that the water coming back from your radiators is hotter than the water going out, which usually means the water isn't flowing correctly through the system.
Your boiler has detected that the water coming back from your radiators is hotter than the water going out, which usually means the water isn't flowing correctly through the system.
What to check first
- Check that all radiator valves are fully open
- Ensure the boiler pressure is between 1 and 1.5 bar on the gauge
- Press and hold the Reset button for five seconds
Parts commonly replaced
- Central heating pump
- Return temperature sensor (NTC)
- Flow temperature sensor (NTC)
E.01 – .17 Your boiler has stopped working because water isn't flowing through the system properly or a temperature sensor has lost its connection.
Your boiler has stopped working because water isn't flowing through the system properly or a temperature sensor has lost its connection.
What to check first
- Locate the reset button or selector switch on the front control panel
- Press and hold the reset button for five seconds
- Check that your radiator valves are open and that the system pressure is between 1 and 1.5 bar
Parts commonly replaced
- NTC Temperature Sensor
- Circulation Pump
- Wiring Harness
Related codes
E.01 – .20 Your boiler has shut down because it is getting too hot inside, likely due to a lack of water flow or a faulty sensor.
Your boiler has shut down because it is getting too hot inside, likely due to a lack of water flow or a faulty sensor.
What to check first
- Check that your boiler pressure is between 1.0 and 1.5 bar
- Ensure all radiator valves and the boiler isolation valves are fully open
- Try resetting the boiler to see if the fault clears
Parts commonly replaced
- Circulation Pump
- Flue Gas NTC Sensor
- Heat Exchanger (Cleaning/Descaling)
E.02 – .00 Your boiler is letting you know that the reset button has been pushed and it is restarting itself.
Your boiler is letting you know that the reset button has been pushed and it is restarting itself.
What to check first
- Wait for the boiler to complete its internal startup checks.
- Monitor the display to see if the numeric temperature or home screen returns.
- If the code persists, try pressing and holding the reset button for 3 seconds.
E.02 – .07 Your boiler has detected that there is not enough water in the heating system to operate safely, causing it to shut down to prevent damage.
Your boiler has detected that there is not enough water in the heating system to operate safely, causing it to shut down to prevent damage.
What to check first
- Locate the filling loop (usually a silver braided hose with small valves under or near the boiler).
- Slowly open the valve or valves until you hear water entering the system.
- Watch the pressure gauge and close the valves once it reaches between 1.0 and 1.5 bar.
Parts commonly replaced
- Filling loop
- Expansion vessel re-pressurisation
- Pressure sensor
E.02 – .16 Your boiler's main control system has stopped communicating internally or has suffered an electrical failure, meaning it cannot start the heating process.
Your boiler's main control system has stopped communicating internally or has suffered an electrical failure, meaning it cannot start the heating process.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Internal wiring harness
E.02 – .17 Your boiler has developed a communication failure between its internal computer and the gas control unit, meaning it cannot safely manage the fuel needed to produce heat or hot water.
Your boiler has developed a communication failure between its internal computer and the gas control unit, meaning it cannot safely manage the fuel needed to produce heat or hot water.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Gas Valve
- Wiring Harness
Related codes
E.02 – .19 Your boiler’s internal control board settings have been altered or are misconfigured, preventing it from operating correctly.
Your boiler’s internal control board settings have been altered or are misconfigured, preventing it from operating correctly.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- PCB Jumper Link
E.02 – .20 Your boiler's internal computer settings have been changed or are set incorrectly, causing it to stop for safety.
Your boiler's internal computer settings have been changed or are set incorrectly, causing it to stop for safety.
Parts commonly replaced
- Main PCB (Printed Circuit Board)
- Jumper Link
Showing 51–60 of 129
E.02 – .21 Your boiler's internal settings have been adjusted incorrectly, meaning the control board doesn't know which model it is currently operating.
Your boiler's internal settings have been adjusted incorrectly, meaning the control board doesn't know which model it is currently operating.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Configuration Jumper
E.02 – .47 Your boiler is having trouble communicating with an external control, like your thermostat or a smart heating box, due to a wiring issue.
Your boiler is having trouble communicating with an external control, like your thermostat or a smart heating box, due to a wiring issue.
Parts commonly replaced
- External control wiring
- Receiver box
- Room thermostat
E.02 – .48 Your boiler is having trouble communicating with your wireless thermostat or smart home controller.
Your boiler is having trouble communicating with your wireless thermostat or smart home controller.
What to check first
- Check that your wireless thermostat or hub has power and fresh batteries.
- Move the thermostat closer to the boiler to see if signal interference is the cause.
- Follow the manufacturer instructions to re-pair or 're-sync' the thermostat to the boiler receiver.
Parts commonly replaced
- Wireless Receiver
- Smart Thermostat
- RF Module
E.04 – .00 Your boiler has stopped working because it cannot communicate with the internal part that controls the gas supply.
Your boiler has stopped working because it cannot communicate with the internal part that controls the gas supply.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
- Wiring Harness
E.04 – .01 Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit due to a faulty internal sensor or wiring.
Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit due to a faulty internal sensor or wiring.
Parts commonly replaced
- Flow Temperature Sensor (NTC Thermistor)
- Wiring Harness
E.04 – .02 Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit, usually due to a faulty sensor or a loose internal wire.
Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit, usually due to a faulty sensor or a loose internal wire.
Parts commonly replaced
- Flow Temperature Sensor (NTC Thermistor)
- Wiring Harness
E.04 – .03 Your boiler has reached an unsafe temperature because water is not moving through the unit properly, causing it to shut down to prevent damage.
Your boiler has reached an unsafe temperature because water is not moving through the unit properly, causing it to shut down to prevent damage.
What to check first
- Check that all radiator valves (TRVs) are turned to the highest setting.
- Ensure the external magnetic filter or any isolation valves under the boiler are fully open.
- Check your system pressure on the gauge and top up to 1.5 bar if it is low.
Parts commonly replaced
- Circulating Pump
- Heat Exchanger (De-sludging)
- Flow Temperature Sensor
Related codes
E.04 – .04 Your boiler has stopped working because it cannot correctly measure the temperature of the exhaust gases leaving the system.
Your boiler has stopped working because it cannot correctly measure the temperature of the exhaust gases leaving the system.
Parts commonly replaced
- Flue temperature sensor (NTC)
- Wiring harness
- Main circuit board (PCB)
Related codes
E.04 – .05 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.
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.
Parts commonly replaced
- Flue Gas NTC Sensor
- Wiring Harness
- Main Control Board
Related codes
E.04 – .06 Your boiler has shut down because it is overheating or has detected a blockage in the chimney flue.
Your boiler has shut down because it is overheating or has detected a blockage in the chimney flue.
Parts commonly replaced
- Flue Gas NTC Sensor
- Heat Exchanger
- Water Pump
Showing 61–70 of 129
E.04 – .08 Your boiler has overheated or detects a lack of water circulation, causing it to shut down for safety.
Your boiler has overheated or detects a lack of water circulation, causing it to shut down for safety.
What to check first
- Check if your radiator valves are open
- Ensure the system pressure is between 1.0 and 1.5 bar on the gauge
- Try resetting the boiler using the selector switch
Parts commonly replaced
- Safety Thermostat (Limit Statutory)
- Circulation Pump
- NTC Temperature Sensor
E.04 – .10 Your boiler is failing to ignite, which means it cannot start the burner to provide you with heating or hot water.
Your boiler is failing to ignite, which means it cannot start the burner to provide you with heating or hot water.
What to check first
- Check if your gas supply is active by testing another gas appliance like a hob
- Ensure your gas meter has credit if you use a pre-payment meter
- Press and hold the 'R' or Reset button for 5 seconds
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Flame Sensing Electrode
E.04 – .12 Your boiler's internal safety sensors are detecting a flame when there shouldn't be one, or the burner is becoming dangerously overheated.
Your boiler's internal safety sensors are detecting a flame when there shouldn't be one, or the burner is becoming dangerously overheated.
Parts commonly replaced
- Ionisation Electrode
- Gas Valve
- Printed Circuit Board (PCB)
- Burner Door Seal
E.04 – .13 Your boiler's fan has stopped spinning, which means it cannot safely remove exhaust gases and has shut down as a precaution.
Your boiler's fan has stopped spinning, which means it cannot safely remove exhaust gases and has shut down as a precaution.
Parts commonly replaced
- Fan assembly
- Wiring harness
- Main PCB
Related codes
E.04 – .17 Your boiler has detected a serious electronic or internal mechanical failure within the gas supply system and has shut down for safety.
Your boiler has detected a serious electronic or internal mechanical failure within the gas supply system and has shut down for safety.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
- Venturi/Air Unit
E0 Your boiler's internal thermometer has stopped working correctly, meaning the system doesn't know how hot the water is and has shut down as a precaution.
Your boiler's internal thermometer has stopped working correctly, meaning the system doesn't know how hot the water is and has shut down as a precaution.
Parts commonly replaced
- NTC Temperature Sensor
- Sensor Wiring Harness
Related codes
E1 Your boiler has become too hot and has shut down as a safety precaution to prevent damage.
Your boiler has become too hot and has shut down as a safety precaution to prevent damage.
What to check first
- Turn off the boiler and allow it to cool down completely.
- Use a radiator key to bleed any trapped air from all radiators in your home.
- Check your boiler pressure gauge and top it up to between 1.0 and 1.5 bar if it has dropped.
- Press the reset button on the boiler control panel.
Parts commonly replaced
- Overheat Thermostat
- Circulation Pump
- Temperature Sensor (NTC)
Related codes
E2 Your boiler is struggling to move water through the system, which is usually caused by trapped air or a blockage preventing proper heating.
Your boiler is struggling to move water through the system, which is usually caused by trapped air or a blockage preventing proper heating.
What to check first
- Turn off your heating and let the radiators cool down.
- Use a radiator key to bleed air from all radiators, starting with the downstairs ones.
- Check your boiler pressure gauge and top it up to between 1.0 and 1.5 bar if it has dropped.
Parts commonly replaced
- Circulation Pump
- Flow Temperature Sensor
- Auto Air Vent
Related codes
E3 Your boiler's internal computer has developed a fault and can no longer control the heating system safely.
Your boiler's internal computer has developed a fault and can no longer control the heating system safely.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Wiring Harness
E4 Your boiler is struggling to light because there might be trapped air in the system or a temporary lack of gas supply.
Your boiler is struggling to light because there might be trapped air in the system or a temporary lack of gas supply.
What to check first
- Check that your gas meter has credit and the isolation valve is open.
- Turn the selector switch to the 'R' (Reset) position for at least five seconds.
- Bleed your radiators using a radiator key to remove any trapped air pockets.
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Spark Lead
Related codes
Showing 71–80 of 129
E09 Your boiler has lost its electronic connection to the gas supply valve, meaning it cannot ignite to provide heating or hot water.
Your boiler has lost its electronic connection to the gas supply valve, meaning it cannot ignite to provide heating or hot water.
Parts commonly replaced
- Gas valve wiring harness
- Gas valve
- Printed Circuit Board (PCB)
Related codes
E10 Your boiler has lost communication with the sensor that measures the temperature outside, which helps it run more efficiently.
Your boiler has lost communication with the sensor that measures the temperature outside, which helps it run more efficiently.
Parts commonly replaced
- Outdoor weather compensation sensor
- Sensor wiring
Related codes
E12 Your boiler has stopped working because it cannot detect that water is circulating through the system correctly.
Your boiler has stopped working because it cannot detect that water is circulating through the system correctly.
What to check first
- Check that your system pressure is between 1.0 and 1.5 bar on the pressure gauge
- If pressure is low, use the filling loop to top it up
- Ensure all radiator valves are open and not blocked by air
- Reset the boiler once the pressure is corrected
Parts commonly replaced
- Differential pressure switch
- Circulating pump
- Diaphragm
Related codes
E13 Your boiler has detected that a internal water sensor is stuck in the 'on' position even though the pump has stopped, preventing the system from restarting safely.
Your boiler has detected that a internal water sensor is stuck in the 'on' position even though the pump has stopped, preventing the system from restarting safely.
Parts commonly replaced
- Differential pressure switch
- Diaphragm
- System pump
Related codes
E15 Your boiler has detected an internal electrical communication error between the main control board and the gas valve, preventing it from lighting safely.
Your boiler has detected an internal electrical communication error between the main control board and the gas valve, preventing it from lighting safely.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
- Wiring Harness
Related codes
E20 Your boiler's internal thermometer for the heating system has developed a fault or is disconnected, meaning the unit cannot accurately measure water temperature to run safely.
Your boiler's internal thermometer for the heating system has developed a fault or is disconnected, meaning the unit cannot accurately measure water temperature to run safely.
Parts commonly replaced
- Central heating NTC temperature sensor
- NTC wiring harness
Related codes
E28 Your boiler has detected a problem with how it releases exhaust gases or a blockage in the drainage system, causing it to shut down for safety.
Your boiler has detected a problem with how it releases exhaust gases or a blockage in the drainage system, causing it to shut down for safety.
What to check first
- Check the external flue pipe outside your home for obstructions like bird nests or debris.
- Inspect the white plastic condensate pipe outside for signs of freezing or blockages.
- If the condensate pipe is frozen, gently pour warm (not boiling) water over it to thaw it.
- Reset the boiler once to see if the fault clears.
Parts commonly replaced
- Flue NTC Sensor
- Air Pressure Switch
- Condensate Trap
Related codes
E40 Your boiler's internal sensor that monitors the temperature of the water returning from your radiators has developed a fault or is sending incorrect readings.
Your boiler's internal sensor that monitors the temperature of the water returning from your radiators has developed a fault or is sending incorrect readings.
Parts commonly replaced
- Return NTC thermistor
- Connecting wiring harness
Related codes
E50 Your boiler's temperature sensor for hot water is sending an incorrect signal, meaning the system cannot safely heat your water to the right temperature.
Your boiler's temperature sensor for hot water is sending an incorrect signal, meaning the system cannot safely heat your water to the right temperature.
Parts commonly replaced
- Domestic Hot Water (DHW) NTC thermistor
- Connecting wiring harness
Related codes
E53 Your boiler has detected that waste gases are not leaving the system properly or the air supply is restricted, causing the burner to shut down for safety.
Your boiler has detected that waste gases are not leaving the system properly or the air supply is restricted, causing the burner to shut down for safety.
What to check first
- Check the flue terminal on the outside of your property for any obstructions like bird nests, leaves, or debris.
- Remove any snow or ice buildup from the flue pipe if it is a particularly cold day.
- Reset the boiler by following the instructions in your user manual once the obstruction is cleared.
Parts commonly replaced
- Flue ducting
- Gas valve
- Printed Circuit Board (PCB)
Related codes
Showing 81–90 of 129
E54 Your boiler is having trouble detecting when you turn on your hot taps, which may prevent the water from heating up.
Your boiler is having trouble detecting when you turn on your hot taps, which may prevent the water from heating up.
Parts commonly replaced
- DHW Flow Sensor
- Wiring Harness
- Turbine/Flow Switch
Related codes
E55 Your boiler has gone into a safety mode because its internal sensors need to be recalibrated to ensure the gas is burning correctly.
Your boiler has gone into a safety mode because its internal sensors need to be recalibrated to ensure the gas is burning correctly.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
- Electrode
Related codes
E78 Your boiler is struggling to accurately detect the water balance in the system, which is preventing it from heating your home safely.
Your boiler is struggling to accurately detect the water balance in the system, which is preventing it from heating your home safely.
Parts commonly replaced
- Water pressure sensor
- Sensor wiring harness
Related codes
E83/E84/E85/E86/E87 Your boiler's internal computer has lost contact with its control sensors or external thermostat, meaning it cannot receive the instructions needed to heat your home.
Your boiler's internal computer has lost contact with its control sensors or external thermostat, meaning it cannot receive the instructions needed to heat your home.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Communication Cable
- External Controls Receiver
E92 Your boiler has failed an automatic internal safety check while trying to adjust its own combustion levels.
Your boiler has failed an automatic internal safety check while trying to adjust its own combustion levels.
Parts commonly replaced
- Gas Valve
- PCB (Printed Circuit Board)
- Electrode Set
Related codes
E100 Your boiler's internal computer has lost track of the correct time, which may prevent it from following your heating schedule.
Your boiler's internal computer has lost track of the correct time, which may prevent it from following your heating schedule.
What to check first
- Navigate to the main menu on the boiler control panel
- Select the clock or settings option
- Manually reset the current time and date
- Press the reset button to clear the fault code
Parts commonly replaced
- None (Software reset)
- Printed Circuit Board (PCB) if fault persists
E109 Your boiler is struggling to move water through the system properly, which is causing it to stop running to prevent overheating.
Your boiler is struggling to move water through the system properly, which is causing it to stop running to prevent overheating.
What to check first
- Check that the boiler pressure is between 1 and 1.5 bar on the pressure gauge
- Ensure all radiator valves are fully open
- Check for any visible leaks around the boiler or pipework
Parts commonly replaced
- Circulation pump
- Main heat exchanger
- Flow and return thermistors
Related codes
E110 Your boiler has likely overheated, causing a safety sensor to shut it down to prevent damage.
Your boiler has likely overheated, causing a safety sensor to shut it down to prevent damage.
What to check first
- Allow the boiler to cool down for 20 to 30 minutes
- Check that your radiator valves are open and not blocked
- Press and hold the 'R' or Reset button for five seconds
Parts commonly replaced
- Overheat Thermostat
- Circulating Pump
- Temperature Sensors (NTC)
Related codes
E117 Your boiler has detected that there is too much water pressure in the system, which causes it to shut down as a safety precaution.
Your boiler has detected that there is too much water pressure in the system, which causes it to shut down as a safety precaution.
What to check first
- Locate a radiator and attach a bleed key to the valve.
- Slowly open the valve to release a small amount of water into a container or cloth.
- Monitor the boiler pressure gauge until it falls back into the green zone (typically 1.0 to 1.5 bar) and then tighten the valve.
Parts commonly replaced
- Filling loop valve
- Expansion vessel
- Pressure relief valve
Related codes
E118 Your boiler has stopped working because the water pressure inside the system has dropped too low and needs to be topped up.
Your boiler has stopped working because the water pressure inside the system has dropped too low and needs to be topped up.
What to check first
- Locate the filling loop (usually a silver flexible hose with small tap handles) underneath your boiler.
- Slowly open both taps until you hear water entering the system.
- Watch the pressure gauge and close both taps tightly once the needle reaches between 1 and 1.5 bar.
Parts commonly replaced
- Filling loop
- Expansion vessel
- Pressure relief valve
Related codes
Showing 91–100 of 129
E119 Your boiler has stopped working because the water pressure inside the system is too low.
Your boiler has stopped working because the water pressure inside the system is too low.
What to check first
- Locate the filling loop (the flexible silver hose) underneath or near the boiler.
- Slowly open the valve or valves on the loop until you hear water flowing.
- Watch the pressure gauge and close the valves once the needle reaches between 1.0 and 1.5 bar.
Parts commonly replaced
- Filling loop
- Water pressure switch
- Expansion vessel
Related codes
E125 Your boiler has detected that water is not moving around the system properly, which is causing it to overheat and shut down for safety.
Your boiler has detected that water is not moving around the system properly, which is causing it to overheat and shut down for safety.
What to check first
- Check that your silver radiator valves (TRVs) are turned up and not all closed at once.
- Inspect your system pressure gauge and top it up to 1.5 bar if it is too low.
- Gently bleed your radiators to remove any trapped air pockets.
Parts commonly replaced
- Circulation pump
- Flow temperature sensor
- Return temperature sensor
Related codes
E128 Your boiler is struggling to keep its burner lit consistently and has shut down for safety after multiple failed attempts.
Your boiler is struggling to keep its burner lit consistently and has shut down for safety after multiple failed attempts.
Parts commonly replaced
- Flame sensing electrode
- Ignition lead
- Gas valve
- Printed Circuit Board (PCB)
Related codes
E129 Your boiler is struggling to keep a steady flame while it tries to automatically adjust its settings, causing it to stop for safety.
Your boiler is struggling to keep a steady flame while it tries to automatically adjust its settings, causing it to stop for safety.
Parts commonly replaced
- Flame sensing electrode
- Ignition lead
- Gas valve
- Printed Circuit Board (PCB)
Related codes
E130 Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution.
Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution.
Parts commonly replaced
- Flue NTC Sensor
- Main Heat Exchanger cleaning
- Wiring harness
Related codes
E131 Your boiler has switched itself off because the temperature in the exhaust pipe has become too hot to operate safely.
Your boiler has switched itself off because the temperature in the exhaust pipe has become too hot to operate safely.
Parts commonly replaced
- Heat exchanger
- Flue thermistor
- Condensate trap
- Debris or blockage removal
Related codes
E133 Your boiler has failed to light because it either cannot get enough gas or cannot detect a flame.
Your boiler has failed to light because it either cannot get enough gas or cannot detect a flame.
What to check first
- Check if other gas appliances like your hob are working to confirm your gas supply is active.
- If you have a prepaid meter, ensure you have credit.
- Hold the reset button for five seconds to see if the boiler restarts.
- If it is freezing outside, check that your white condensate pipe is not frozen.
Parts commonly replaced
- Gas Valve
- Ignition Lead and Electrode
- Printed Circuit Board (PCB)
Related codes
E134 Your boiler has tried to ignite several times but cannot establish a steady flame, often because the gas supply is interrupted or the ignition system is failing.
Your boiler has tried to ignite several times but cannot establish a steady flame, often because the gas supply is interrupted or the ignition system is failing.
What to check first
- Check that your gas emergency control valve is 'Open' and your gas meter has credit.
- Try to light another gas appliance, such as a hob, to confirm gas is reaching the property.
- Reset the boiler by turning the selector switch to the reset position for five seconds.
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Printed Circuit Board (PCB)
Related codes
E135 Your boiler has stopped working because it cannot detect a steady gas supply or has encountered an internal communication error regarding the gas valve.
Your boiler has stopped working because it cannot detect a steady gas supply or has encountered an internal communication error regarding the gas valve.
What to check first
- Check if other gas appliances in your home, like a hob, are still working to rule out a general supply issue.
- Ensure your gas meter has credit if you are on a prepay system.
- Try resetting the boiler by turning the selector switch to 'R' for five seconds and then back to the run position.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
- Ignition Electrode
Related codes
E154 Your boiler has noticed that water isn't moving through the system quickly enough, causing the temperature to rise too fast.
Your boiler has noticed that water isn't moving through the system quickly enough, causing the temperature to rise too fast.
Parts commonly replaced
- Circulation Pump
- Flow Temperature Sensor
- Return Temperature Sensor
Related codes
Showing 101–110 of 129
E160 Your boiler's fan, which safely pushes exhaust fumes out of the house, has stopped spinning or isn't communicating with the main control board.
Your boiler's fan, which safely pushes exhaust fumes out of the house, has stopped spinning or isn't communicating with the main control board.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
- Fan wiring harness
Related codes
E160 / E161 Your boiler has detected a problem with the fan that safely clears away exhaust gases, meaning the system has shut down as a safety precaution.
Your boiler has detected a problem with the fan that safely clears away exhaust gases, meaning the system has shut down as a safety precaution.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
E163 Your boiler's temperature sensor for hot water has stopped working correctly, meaning your taps may not get warm or the temperature could be inconsistent.
Your boiler's temperature sensor for hot water has stopped working correctly, meaning your taps may not get warm or the temperature could be inconsistent.
Parts commonly replaced
- DHW NTC thermistor sensor
- Wiring harness
- Main PCB
Related codes
E164 Your boiler is having trouble measuring its internal water pressure, which prevents it from running safely to provide heating and hot water.
Your boiler is having trouble measuring its internal water pressure, which prevents it from running safely to provide heating and hot water.
Parts commonly replaced
- Water pressure sensor
- Wiring harness
- Main PCB
Related codes
E167 Your boiler's computer control board has encountered an internal error and can no longer safely operate the system.
Your boiler's computer control board has encountered an internal error and can no longer safely operate the system.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
Related codes
E168 Your boiler's internal computer has crashed or is confused, causing the system to shut down for safety.
Your boiler's internal computer has crashed or is confused, causing the system to shut down for safety.
What to check first
- Locate the reset button or selector switch on the front of the boiler
- Turn the dial to 'R' or press the reset button for 5 seconds
- Check if the household electricity supply or 'smart' plugs are causing any interference
Parts commonly replaced
- Printed Circuit Board (PCB)
- External Power Surge Protector
- Wiring Loom
Related codes
E193 Your boiler has sensed that water is not moving through the internal pipes quickly enough before the burner starts, often caused by a blockage or air trapped in the system.
Your boiler has sensed that water is not moving through the internal pipes quickly enough before the burner starts, often caused by a blockage or air trapped in the system.
What to check first
- Check that all radiator valves are fully open
- Ensure the boiler pressure is between 1 and 1.5 bar on the gauge
- Gently bleed your radiators to remove any trapped air
- Switch the boiler off and on again to reset the system
Parts commonly replaced
- Circulation Pump
- Flow Temperature Sensor
- Automatic Air Vent
Related codes
E270 Your boiler has detected that water isn't moving through the system properly, which is causing it to overheat too quickly.
Your boiler has detected that water isn't moving through the system properly, which is causing it to overheat too quickly.
What to check first
- Check that your central heating valves (under the boiler) are fully open
- Ensure all radiator valves (TRVs) are turned to the highest setting
- Check if the system pressure gauge is between 1 and 1.5 bar and top up if low
- Try resetting the boiler to see if the air clears naturally
Parts commonly replaced
- Central heating pump
- Main heat exchanger (descale)
- Flow or Return thermistor
Related codes
E317 Your boiler is detects an issue with the electrical power supply coming into your home, meaning the electrical timing does not match what the unit needs to operate.
Your boiler is detects an issue with the electrical power supply coming into your home, meaning the electrical timing does not match what the unit needs to operate.
Parts commonly replaced
- Main PCB
- External Voltage Regulator
E321 Your boiler's hot water sensor is not reading the temperature correctly, which is preventing the system from heating your water safely.
Your boiler's hot water sensor is not reading the temperature correctly, which is preventing the system from heating your water safely.
Parts commonly replaced
- Domestic Hot Water (DHW) NTC thermistor
- Connecting wiring harness
Related codes
Showing 111–120 of 129
E384 Your boiler thinks there is a flame present when there shouldn't be, causing the system to shut down for safety.
Your boiler thinks there is a flame present when there shouldn't be, causing the system to shut down for safety.
Parts commonly replaced
- Flame sensing electrode
- Gas valve
- Printed Circuit Board (PCB)
Related codes
E385 Your boiler has stopped working because the electrical supply to it has dropped too low to operate the internal components safely.
Your boiler has stopped working because the electrical supply to it has dropped too low to operate the internal components safely.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Internal Wiring Harness
- External Voltage Regulator
Related codes
E430 Your boiler is performing a routine check to ensure there is enough water pressure in the system to operate safely.
Your boiler is performing a routine check to ensure there is enough water pressure in the system to operate safely.
What to check first
- Check the pressure gauge on the front of the boiler or under the casing.
- If the pressure is below 1.0 bar, use the filling loop handles to top it up to 1.5 bar.
- Restart the boiler to see if the message clears.
Parts commonly replaced
- External filling loop
- Water pressure sensor
Related codes
H.01 – .00 Your boiler has lost its connection with the internal gas control system, meaning it cannot safely ignite to provide heating or hot water.
Your boiler has lost its connection with the internal gas control system, meaning it cannot safely ignite to provide heating or hot water.
Parts commonly replaced
- Gas valve
- Main PCB
- Wiring harness
H.01 – .05 Your boiler is struggling to move water around the system properly, causing it to heat up too quickly and shut down as a safety precaution.
Your boiler is struggling to move water around the system properly, causing it to heat up too quickly and shut down as a safety precaution.
What to check first
- Check that all radiator valves are fully open
- Ensure your system pressure is between 1.0 and 1.5 bar
- Bleed all radiators to remove trapped air pockets
Parts commonly replaced
- Circulation Pump
- Temperature Sensors (NTC Thermistors)
- Main Heat Exchanger (if blocked)
Related codes
H.01 – .08 Your boiler is heating up too quickly or water isn't moving through the system properly, causing it to shut down to prevent overheating.
Your boiler is heating up too quickly or water isn't moving through the system properly, causing it to shut down to prevent overheating.
What to check first
- Check that all radiator valves are fully open
- Ensure your system pressure is between 1.0 and 1.5 bar on the gauge
- Check for any visible leaks or air locks and bleed your radiators
Parts commonly replaced
- Circulation Pump
- Flow Temperature Sensor (NTC)
- Main Heat Exchanger
Related codes
H.01 – .14 Your boiler has detected that it is getting too hot too quickly, usually because water isn't moving through the system properly.
Your boiler has detected that it is getting too hot too quickly, usually because water isn't moving through the system properly.
What to check first
- Check that your radiator valves are open
- Ensure your system pressure is between 1 and 1.5 bar on the gauge
- Bleed your radiators to remove any trapped air
- Reset the boiler to see if the temporary fault clears
Parts commonly replaced
- Circulation Pump
- Central Heating Filter (Cleaning)
- Flow Temperature Sensor
Related codes
H.01 – .18 Your boiler is struggling to move water through the system, which is causing it to shut down to prevent overheating.
Your boiler is struggling to move water through the system, which is causing it to shut down to prevent overheating.
What to check first
- Check that the boiler pressure gauge is between 1 and 1.5 bar
- Ensure all radiator valves and the isolation valves under the boiler are fully open
- Bleed your radiators to remove any trapped air pockets
Parts commonly replaced
- Circulation pump
- Flow and return temperature sensors (NTC thermistors)
- Main heat exchanger
Related codes
H.01 – .21 Your boiler is heating up too quickly when you turn on the hot water, causing it to shut down to prevent overheating.
Your boiler is heating up too quickly when you turn on the hot water, causing it to shut down to prevent overheating.
What to check first
- Check that your main water stopcock is fully open
- Ensure all isolation valves under the boiler are in the open position
- Switch the boiler off and back on again at the fused spur to reset the system
Parts commonly replaced
- DHW Temperature Sensor (NTC)
- Plate Heat Exchanger
- Circulation Pump
H.02 – .02 Your boiler’s internal computer card hasn't been programmed correctly, or it has forgotten its basic settings, meaning it doesn't know how to operate your specific heating system.
Your boiler’s internal computer card hasn't been programmed correctly, or it has forgotten its basic settings, meaning it doesn't know how to operate your specific heating system.
Parts commonly replaced
- Printed Circuit Board (PCB)
Showing 121–129 of 129
H.02 – .03 Your boiler is having a temporary 'handshake' issue where its internal control settings don't quite match what the hardware expects, usually following a power cut or a recent service.
Your boiler is having a temporary 'handshake' issue where its internal control settings don't quite match what the hardware expects, usually following a power cut or a recent service.
What to check first
- Locate the reset button or selector switch on the front of the control panel.
- Press and hold the reset button for at least 5 seconds, then release.
- Wait for the boiler to complete its startup sequence; if the code clears, use the heating as normal.
Parts commonly replaced
- None (Software reset)
- Main PCB (if error persists)
H.02 – .04 Your boiler's computer system is experiencing a temporary communication glitch with its internal settings.
Your boiler's computer system is experiencing a temporary communication glitch with its internal settings.
What to check first
- Locate the Reset button on the boiler control panel.
- Press and hold the Reset button for 5 seconds.
- Wait for the boiler to complete its restart sequence to see if the error clears.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
H.02 – .06 Your boiler has detected that the water pressure is too low for it to run safely, or there is a possible leak in the system.
Your boiler has detected that the water pressure is too low for it to run safely, or there is a possible leak in the system.
What to check first
- Check your boiler's pressure gauge to see if it is below 1 bar.
- Locate the filling loop (usually a silver braided hose with small valves) and slowly top up the water pressure to 1.5 bar.
- Check your radiators and visible pipework for any signs of water leaks.
Parts commonly replaced
- Pressure Sensor
- Expansion Vessel
- Filling Loop Valve
Related codes
H.03 -.00 Your boiler is struggling to communicate with its internal temperature sensors, which is preventing it from heating up safely.
Your boiler is struggling to communicate with its internal temperature sensors, which is preventing it from heating up safely.
Parts commonly replaced
- NTC Temperature Sensor
- Flue Sensor
- Wiring Harness
Related codes
H.03 – .01 Your boiler's internal computer parts are struggling to talk to each other, which prevents the system from starting up.
Your boiler's internal computer parts are struggling to talk to each other, which prevents the system from starting up.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Wiring Harness
- Display Interface
Related codes
H.03 – .02 Your boiler has lost its flame while it was running, meaning it cannot provide heat or hot water and has shut down for safety.
Your boiler has lost its flame while it was running, meaning it cannot provide heat or hot water and has shut down for safety.
What to check first
- Check that your gas prepay meter has credit
- Ensure other gas appliances (like a hob) are working to confirm gas supply
- Press and hold the 'R' or Reset button for five seconds
Parts commonly replaced
- Flame sensing electrode
- Gas valve
- Ignition lead
Related codes
OFF OFF OFF Your boiler has lost electrical power entirely and the screen is blank because it is not receiving any electricity.
Your boiler has lost electrical power entirely and the screen is blank because it is not receiving any electricity.
What to check first
- Check if other appliances in your home are working to rule out a general power cut.
- Ensure the boiler’s main power switch (usually a white fused spur near the boiler) is turned on.
- Check your home's main fuse box (consumer unit) to see if any circuit breakers have tripped or moved to the 'off' position.
Parts commonly replaced
- External fuse
- Internal PCB fuse
- Printed Circuit Board (PCB)
ON OFF ON Your boiler has failed to light three times and has locked itself out for safety reasons.
Your boiler has failed to light three times and has locked itself out for safety reasons.
What to check first
- Check that your gas supply is turned on and that other gas appliances are working.
- Ensure you have credit on your prepaid gas meter, if applicable.
- Restart the boiler by switching the selector switch to 'Reset' for five seconds before turning it back to the 'On' position.
Parts commonly replaced
- Ignition electrode
- Gas valve
- Printed Circuit Board (PCB)
Related codes
ON ON ON Your boiler has detected a communication problem between its internal electronic components, meaning it cannot operate safely.
Your boiler has detected a communication problem between its internal electronic components, meaning it cannot operate safely.
Parts commonly replaced
- Low voltage wiring harness
- Printed Circuit Board (PCB)