Alpha E-Tec Plus 10 / 18 Fault codes & diagnostics

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

System Natural GasLPG 10-18 kW 2019-present
GC Number 47-532-78
Download the Alpha E-Tec Plus 10 / 18 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 26 High 4 Medium 1 Low
Just want the most common Alpha E-Tec Plus 10 / 18 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 32 documented codes

Tap any card for details

01

Your boiler has failed to light the gas, meaning it cannot heat your water or radiators.

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is active by testing another gas appliance like a hob.
  2. Check your gas meter to ensure it has credit or the valve is turned on.
  3. Press and hold the 'R' reset button for 2 seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ignition Lead
  • Fan

Related codes

Full explanation for 01
02

Your boiler has shut down because it has detected it is getting too hot, which is usually due to a lack of water flow through the system.

High DIY-safe £120-350

What to check first

  1. Check that your radiator valves are open to ensure water can move freely.
  2. Check the boiler pressure gauge and top it up to 1.5 bar if it is low.
  3. Attempt to reset the boiler by turning the selector knob to the 'R' position for 5 seconds.
  4. Bleed your radiators to remove any trapped air that might be causing a blockage.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger (if scaled up)

Related codes

Full explanation for 02
03

Your boiler has switched itself off because the waste gases are getting too hot, which is a safety mechanism to prevent internal damage.

Emergency Engineer only £120-350

Parts commonly replaced

  • Flue Thermistor
  • Heat Exchanger cleaning
  • Main Heat Exchanger

Related codes

Full explanation for 03
04

Your boiler has detected an electrical communication problem with the internal gas valve, which means it cannot safely ignite to provide heating or hot water.

High Engineer only £160-£350

Parts commonly replaced

  • Gas Valve
  • Wiring Harness
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 04
05

Your boiler has detected a problem with the sensor that monitors the temperature of the water leaving the unit, meaning it cannot operate safely or effectively.

High Engineer only £90-160

Parts commonly replaced

  • Flow NTC temperature sensor
  • Wiring harness

Related codes

Full explanation for 05
06

Your boiler has detected a fault with the sensor that manages your hot water temperature, meaning you likely have no hot water or the temperature is inconsistent.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Sensor
  • Sensor wiring harness

Related codes

Full explanation for 06
08

Your boiler has been manually reset too many times in a short period and has now locked itself out for safety.

High DIY-safe £0-120

What to check first

  1. Turn the power supply to the boiler off at the fused spur switch
  2. Wait for 30 seconds
  3. Turn the power back on to clear the reset limit

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Electrode
  • Gas Valve

Related codes

Full explanation for 08
10

Your boiler has detected that the water pressure is too low for it to operate safely and effectively.

High DIY-safe £0-160

What to check first

  1. Locate the filling loop (usually a silver braided hose underneath the boiler).
  2. Slowly open the valve(s) until you hear water entering the system.
  3. Monitor the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the valves tightly.

Parts commonly replaced

  • Primary pressure switch
  • Filling loop valve
  • Expansion vessel

Related codes

Full explanation for 10
12

Your boiler has detected an issue with a temperature sensor that monitors incoming water, which can affect how efficiently it provides hot water.

Low Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) inlet sensor
  • Wiring harness
Full explanation for 12
15

Your boiler’s internal computer is confused because its software settings do not match the physical parts it is trying to control.

High Engineer only £100-280

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Harness

Related codes

Full explanation for 15
Showing 11–20 of 32
16

Your boiler has stopped working because the internal fan, which safely exhausts fumes, is either not spinning correctly or has lost its electrical connection.

High Engineer only £220-£350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 16
20

Your boiler thinks a flame is present even though no gas should be flowing, which is causing it to shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation Probe
  • Gas Valve
  • Main PCB

Related codes

Full explanation for 20
22

Your boiler's internal computer is experiencing a software error, causing the system to stop working as a safety precaution.

High Engineer only £250-400

Parts commonly replaced

  • Main PCB

Related codes

Full explanation for 22
23

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, which is preventing it from running safely.

High Engineer only £100-180

Parts commonly replaced

  • Return NTC thermistor
  • Sensor wiring harness
  • Main PCB

Related codes

Full explanation for 23
24

One of the buttons on your boiler's control panel has become jammed or is being continuously pressed, which is preventing the system from operating correctly.

High DIY-safe £0-120

What to check first

  1. Identify which button on the front panel feels stuck or stiff.
  2. Gently press and wiggle the affected button to see if it pops back out.
  3. Clean the area around the buttons with a dry, soft cloth to remove any sticky residue or dust.
  4. Reset the boiler using the selector switch.

Parts commonly replaced

  • Control panel fascia
  • PCB (if button contact is damaged)

Related codes

Full explanation for 24
25

Your boiler's internal computer has encountered a software glitch and is unable to operate correctly.

High DIY-safe £250-450

What to check first

  1. Turn the selector switch to the 'Reset' position for a few seconds.
  2. Return the switch to the 'On' position to see if the error clears.
  3. Turn the main power supply to the boiler off at the wall, wait one minute, and turn it back on.

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for 25
27

Your boiler is getting too hot too quickly because water isn't moving through the system properly.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure your boiler pressure is between 1.0 and 1.5 bar on the gauge
  3. Check if any external heating valves or zone valves are stuck closed

Parts commonly replaced

  • Circulation pump
  • Primary heat exchanger
  • Flow/Return thermistors

Related codes

Full explanation for 27
29

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

High Engineer only £120-£200

Parts commonly replaced

  • Flue NTC sensor
  • Wiring harness
  • Main PCB
Full explanation for 29
31

Your boiler has lost its connection with the remote thermostat or controller, meaning they are no longer talking to each other.

Medium DIY-safe £0-120

What to check first

  1. Check if the batteries in your Alpha Climatic control unit need replacing.
  2. Ensure the controller is within range and has not been moved too far from the boiler.
  3. Reset the boiler by turning the selector switch to the 'RESET' position for 5 seconds.

Parts commonly replaced

  • Batteries
  • Alpha Climatic RF Receiver
  • PCB

Related codes

Full explanation for 31
37

Your boiler is not receiving enough electrical power to turn on or run its functions.

High DIY-safe £0-180

What to check first

  1. Check if there is a local power cut or if other appliances in your home are flickering.
  2. Ensure the boiler's fused spur switch is fully turned on.
  3. Check your home's consumer unit (fuse box) to see if a circuit breaker has tripped and flip it back to 'on'.

Parts commonly replaced

  • Fused spur switch
  • Printed Circuit Board (PCB)
  • External voltage stabilizer

Related codes

Full explanation for 37
Showing 21–30 of 32
38

Your boiler started a flame but it went out immediately, so the system is trying to restart itself to get your heating back on.

High DIY-safe £100-£250

What to check first

  1. Check that your gas supply is active (e.g., check other gas appliances or credit on your meter)
  2. Press and hold the 'R' reset button for a few seconds to clear the fault
  3. Ensure the condensate pipe (plastic pipe leading outside) isn't frozen if it is winter

Parts commonly replaced

  • Ionisation probe
  • Ignition electrode
  • Gas valve

Related codes

Full explanation for 38
43

Your boiler is struggling to keep its flame lit, which may be caused by strong winds affecting the flue or a technical issue with the burner.

High Engineer only £90-250

Parts commonly replaced

  • Ionisation probe
  • Spark electrode
  • Gas valve
  • Flue seals

Related codes

Full explanation for 43
45

Your boiler is overheating because the water is not flowing through the system quickly enough.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1.0 and 1.5 bar on the gauge
  3. Restart the boiler using the reset button

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger (flush required)
  • Flow or Return Sensor

Related codes

Full explanation for 45
47

Your boiler is overheating because the exhaust gases are too hot, so it is running at a lower power level to protect itself from damage.

Medium Engineer only £120-300

Parts commonly replaced

  • Flue Thermostat
  • Main Heat Exchanger (Cleaning or Replacement)
  • Burner Insulation

Related codes

Full explanation for 47
51

Your boiler has lost its wireless connection to the external temperature controller, meaning it may not know when to turn on or off.

Medium DIY-safe £0-180

What to check first

  1. Check the batteries in your wall-mounted thermostat or Climatic controller.
  2. Ensure the controller is within range of the boiler and there are no large metal objects blocking the signal.
  3. Try resetting the boiler and re-pairing the transmitter according to your manual.

Parts commonly replaced

  • Climatic controller batteries
  • RF Receiver unit
  • Wireless Transmitter
Full explanation for 51
60

Your boiler's internal pump has stopped circulating water, which means the system cannot heat your radiators or water to prevent itself from overheating.

High Engineer only £220-450

Parts commonly replaced

  • Circulating Pump
  • Pump head
  • Main PCB

Related codes

Full explanation for 60
61

Your boiler is struggling to push water around your radiators, likely because there is trapped air in the pipes or a blockage in the system.

High DIY-safe £90-250

What to check first

  1. Check that all radiator valves are fully open
  2. Carefully bleed all radiators to remove trapped air
  3. Ensure the boiler pressure gauge is between 1.0 and 1.5 bar
  4. Reset the boiler after checking valves and air

Parts commonly replaced

  • None - often resolved by a system flush
  • External heating filter
  • Circulation pump

Related codes

Full explanation for 61
70

Your boiler has detected that water is flowng incorrectly or sensors are giving conflicting readings, often due to a blockage in the system or a wiring issue.

High Engineer only £120-350

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness
  • Main Heat Exchanger

Related codes

Full explanation for 70
75

Your boiler has detected an issue with its internal temperature sensors, meaning it cannot accurately monitor the water heat and has shut down as a precaution.

High Engineer only £120-190

Parts commonly replaced

  • NTC Temperature Sensor
  • Flow or Return Thermistor

Related codes

Full explanation for 75
76

Your boiler has detected a potential electronic fault with its internal temperature sensors, which means it cannot accurately monitor the water heat.

High Engineer only £120-£210

Parts commonly replaced

  • NTC Temperature Sensor
  • Flow/Return Thermistor
  • Wiring Harness

Related codes

Full explanation for 76
Showing 31–32 of 32
E03

Your boiler has detected that the exhaust gases are getting too hot, so it has shut down as a safety precaution to prevent internal damage.

High Engineer only £120-280

Parts commonly replaced

  • Flue thermostat
  • Main heat exchanger
  • Temperature sensor (NTC)

Related codes

Full explanation for E03
E38

Your boiler has lost its flame while running and has shut down as a safety precaution.

High DIY-safe £100-£280

What to check first

  1. Check if other gas appliances (like a hob) are working to ensure gas is reaching the property
  2. Check that your gas meter has credit if you have a prepayment meter
  3. Press and hold the reset button for several seconds to restart the boiler

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve

Related codes

Full explanation for E38
Status & diagnostic codes

24 operating states & engineer diagnostics

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

d0 Diagnostic Your boiler is notifying you that a specific setting for an optional hot water storage tank is currently active, but this does not indicate a system failure. d1 Diagnostic Your boiler has detected an issue with the flame during operation, which has caused it to shut down for safety reasons. d2 Diagnostic The boiler is simply reporting the current temperature of the water as it leaves the unit to heat your home, which is a normal operational status message rather than a breakdown. d3 Diagnostic Your boiler is reporting a reading from the sensor that monitors the temperature of the water being sent to your hot taps, indicating the system is likely not heating your water as expected. d4 Diagnostic Your boiler is simply indicating the current temperature setting for your radiators, rather than showing an error code. d5 Diagnostic Your boiler is simply displaying the current temperature setting for your hot water, rather than indicating a breakdown. d6 Diagnostic Your boiler is struggling to read the outdoor temperature sensor, so it has reverted to using standard internal settings to keep your heating running. d7 Diagnostic Your boiler is struggling to read the temperature of the water coming into the system or your hot water cylinder, which is preventing it from heating your water correctly. d8 Diagnostic Your boiler is struggling to accurately measure the temperature of the water returning from your radiators, which prevents it from heating your home efficiently. d9 Diagnostic Your boiler is displaying a list of its recent internal error history rather than an active problem. d10 Diagnostic Your boiler is currently displaying a menu screen used to clear previous error logs and is not actually reporting a functional breakdown. d11 Diagnostic Your boiler's electronic control system is showing an undefined status, which typically means the internal computer is failing to communicate correctly. d12 Diagnostic Your boiler is reporting a status update regarding the speed setting of the internal water pump, which helps circulate heat around your home. d13 Diagnostic Your boiler has detected an internal configuration or communication error that prevents it from operating correctly. d14 Diagnostic Your boiler is detecting that the water flow through your heating system is too low to operate safely and effectively. d15 Diagnostic This code is just a status update showing your boiler's internal fan speed, rather than an error that requires immediate action. d16 Diagnostic Your boiler has detected an issue with the sensor that monitors the temperature of the gases leaving your home, which is causing it to stop working to ensure your safety. d17 Diagnostic This code is simply a status display showing the current water temperature inside your boiler and is not an error message at all. d18 Diagnostic Your boiler is currently running a special testing mode used to dry out new floor screed, which is an intentional operational setting rather than a system fault. d19 Diagnostic Your boiler is displaying internal software information rather than a fault, which is typically a harmless glitch caused by a temporary communication error with the display. d20 Diagnostic Your boiler has encountered an undefined system error that is not documented by the manufacturer, which usually suggests a software glitch or a communication failure within the control board. d21 Diagnostic Your boiler is displaying a code that is not currently assigned to a specific fault, which usually points to a system communication glitch or a software error. d22 Diagnostic Your boiler is simply reminding you that your annual service is due soon to ensure it continues to run safely and efficiently. Sr Diagnostic Your boiler is simply reminding you that its annual service is now due to ensure it continues to run safely and efficiently.
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