Alpha E-Tec S Fault codes & diagnostics

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

System Natural Gas 2022-present
GC Numbers 41-532-4741-532-4841-532-52
Download the Alpha E-Tec S 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.
23 High 7 Medium
Just want the most common Alpha E-Tec S faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 30 documented codes

Tap any card for details

01

Your boiler is not starting up because it cannot light the gas flame required to heat your water.

High DIY-safe £100-£300

What to check first

  1. Check that your gas emergency control valve is in the open position
  2. If you have a prepayment meter, check that you have sufficient credit
  3. Press and hold the reset button for several seconds to restart the ignition sequence

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame sensing cable

Related codes

Full explanation for 01
02

Your boiler has become too hot and has switched itself off 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 'off' or '0'.
  2. Ensure your system pressure is between 1 and 1.5 bar on the pressure gauge.
  3. Press and hold the 'R' (Reset) button for a few seconds to restart the boiler.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger

Related codes

Full explanation for 02
03

Your boiler has shut down because it detected that the exhaust gases are getting too hot, which is a safety measure to prevent internal damage.

High Engineer only £120-350

Parts commonly replaced

  • Flue thermistor
  • Main heat exchanger
  • Burner electrodes

Related codes

Full explanation for 03
04

Your boiler has stopped working because it cannot communicate with the unit that controls the gas supply.

High Engineer only £140-£320

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 internal sensor that monitors the temperature of the water heading to your radiators, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • CH Flow NTC sensor
  • Wiring harness
  • Main circuit board (PCB)

Related codes

Full explanation for 05
06

Your boiler is confused about whether it is supposed to be heating hot water or just your radiators because of an incorrect internal setting.

High Engineer only £80-120

Parts commonly replaced

  • Main PCB (if settings won't save)

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 for safety reasons.

High DIY-safe £0-120

What to check first

  1. Turn off the power supply to the boiler at the fused spur switch
  2. Wait for approximately 30 to 60 seconds
  3. Turn the power back on to clear the lockout memory
  4. If the boiler locks out again, do not continue resetting and call a professional to find the underlying fault

Parts commonly replaced

  • None (Reset required)
  • Ignition Electrode
  • Gas Valve

Related codes

Full explanation for 08
10

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

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (a flexible silver hose) underneath or near the boiler
  2. Slowly open the valves on the filling loop until you hear water flowing
  3. Watch the pressure gauge and close the valves once the needle reaches 1.5 bar

Parts commonly replaced

  • Filling loop
  • Expansion vessel recharging
  • Pressure switch

Related codes

Full explanation for 10
12

Your boiler is struggling to communicate with your hot water tank’s sensor, meaning it cannot correctly monitor or heat your water supply.

Medium Engineer only £90-180

Parts commonly replaced

  • NTC Cylinder Sensor
  • Sensor wiring harness

Related codes

Full explanation for 12
15

The boiler's control system is incorrectly programmed or thinks the internal plumbing setup is wrong, meaning it cannot operate safely.

High Engineer only £100-£250

Parts commonly replaced

  • Main PCB
  • Internal Wiring Harness

Related codes

Full explanation for 15
Showing 11–20 of 30
16

Your boiler has switched itself off because the internal fan, which safely removes exhaust fumes, is not spinning at the correct speed or has lost power.

High Engineer only £220-£450

Parts commonly replaced

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

Related codes

Full explanation for 16
20

Your boiler thinks a flame is burning when it shouldn't be, causing the system to shut down for safety.

High Engineer only £120-280

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 20
23

Your boiler has detected an issue with the sensor that monitors the water temperature returning to the unit, causing it to stop running for safety.

High Engineer only £120-£190

Parts commonly replaced

  • Return NTC Temperature Sensor
  • Sensor Wiring Harness

Related codes

Full explanation for 23
24

One of the buttons on your boiler's control panel has become stuck, preventing you from changing settings or operating the system correctly.

Medium DIY-safe £100-280

What to check first

  1. Gently press and release each button on the control panel to see if any feel physically stuck or recessed.
  2. Wipe the control panel with a dry, soft cloth to remove any dirt or sticky residue that might be holding a button down.
  3. Switch the boiler off at the fused spur switch for 30 seconds and turn it back on to reset the electronics.

Parts commonly replaced

  • Control Panel User Interface
  • PCB (Printed Circuit Board)

Related codes

Full explanation for 24
25

Your boiler's internal computer is having a communication error, meaning it cannot safely operate or control the heating system.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Full explanation for 25
29

Your boiler has detected an issue with the sensor that monitors the temperature of the gases leaving your flue, causing it to shut down for safety reasons.

High Engineer only £150-250

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness

Related codes

Full explanation for 29
31

Your boiler has lost its connection to your smart thermostat, meaning it cannot receive instructions on when to turn the heating or hot water on.

Medium DIY-safe £100-250

What to check first

  1. Check if your thermostat display is blank and replace its batteries if needed
  2. Turn the boiler off at the fused spur for 60 seconds and switch it back on to force a re-connection
  3. Ensure the signal booster or receiver unit near the boiler is powered on and the status lights are active

Parts commonly replaced

  • Alpha Climatic Receiver
  • PCB
  • Communication wiring harness

Related codes

Full explanation for 31
37

Your boiler is struggling because the electricity supply it is receiving is weaker than it should be.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for 37
38

Your boiler is trying to ignite but cannot detect a stable flame, so it has shut down as a safety precaution.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Flame rectification probe
  • Gas valve

Related codes

Full explanation for 38
43

Your boiler has detected that the burner flame has gone out or failed to ignite, so it has safely shut itself down to prevent gas from building up.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Flame rectification probe
  • Gas valve

Related codes

Full explanation for 43
Showing 21–30 of 30
45

Your boiler is struggling to circulate water properly because there is a significant temperature difference between the water leaving and returning to the unit.

High Engineer only £120-250

Parts commonly replaced

  • Circulation pump
  • System filter
  • Primary heat exchanger
  • NTC thermistors

Related codes

Full explanation for 45
47

Your boiler is limiting its power because it is struggling to move heat away from the burner efficiently.

Medium Engineer only £120-250

Parts commonly replaced

  • System filter
  • Circulating pump
  • Heat exchanger

Related codes

Full explanation for 47
51

Your boiler is temporarily unable to communicate with its wireless room thermostat, meaning it cannot receive signals to turn the heating on or off.

Medium DIY-safe £80-150

What to check first

  1. Check that your wireless thermostat has fresh batteries installed.
  2. Ensure the thermostat is within range of the boiler and has not been moved behind thick walls or metal objects.
  3. Follow the manufacturer's manual to perform a re-pairing process between the thermostat and the boiler receiver.

Parts commonly replaced

  • RF Receiver unit
  • Wireless thermostat
  • PCB

Related codes

Full explanation for 51
60

Your boiler is unable to move water around your heating system effectively because the pump is not operating correctly.

High Engineer only £250-450

Parts commonly replaced

  • Circulating pump
  • Pump wiring harness
  • Printed Circuit Board

Related codes

Full explanation for 60
61

Your boiler's water pump is struggling because it has trapped air inside, preventing it from circulating heat effectively around your home.

Medium Engineer only £90-180

Parts commonly replaced

  • Central heating pump
  • Automatic air vent

Related codes

Full explanation for 61
75

Your boiler is struggling to accurately measure the temperature of the water circulating inside it, so it has stopped working to prevent potential damage.

High Engineer only £150-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

Full explanation for 75
76

Your boiler is unable to read the temperature of the water circulating inside it, so it has safely shut down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

Full explanation for 76
E03

Your boiler has detected that the gases leaving through your flue are too hot, suggesting it is working inefficiently or struggling to vent heat properly.

High Engineer only £150-300

Parts commonly replaced

  • Primary heat exchanger
  • NTC temperature sensor
  • Flue assembly seals

Related codes

Full explanation for E03
E12

Your boiler has lost the signal from the sensor that monitors the temperature of your hot water cylinder, meaning it may struggle to heat your stored hot water correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • Cylinder NTC sensor
  • Wiring harness

Related codes

Full explanation for E12
E38

Your boiler is failing to stay lit because it cannot detect a flame, causing it to shut down for safety reasons.

High Engineer only £120-250

Parts commonly replaced

  • Flame rectification electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E38
Status & diagnostic codes

17 operating states & engineer diagnostics

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

d1 Diagnostic Your boiler is struggling to detect the flame needed to heat your water and has switched itself off for safety. d2 Diagnostic The code 'd2' is not a fault; it is simply a status display showing the current temperature of the water flowing out of your boiler into your radiators. d4 Diagnostic This code is simply showing you the current temperature setting for your radiators, rather than indicating a fault with your boiler. d5 Diagnostic This code is simply showing you the current temperature setting for your hot water, rather than indicating a fault with your boiler. d6 Diagnostic The boiler is struggling to read the outdoor temperature from a sensor installed outside your home, so it is using a default setting to keep your heating running. d7 Diagnostic Your boiler is having trouble communicating with the temperature sensor in your hot water cylinder, which may result in a lack of hot water. d8 Diagnostic Your boiler is simply displaying the current temperature of the water returning to the system, rather than indicating an actual fault. d9 Diagnostic Your boiler is displaying its saved record of past issues, rather than indicating a current problem. d10 Diagnostic Your boiler is currently displaying its stored history of past technical issues rather than an active fault. d12 Diagnostic Your boiler is simply displaying the current operating speed of the water pump, which is a normal status message rather than a fault code. d14 Diagnostic Your boiler is detecting a very low flow of water through your heating system, which usually means the system is blocked or the pump is struggling to circulate water. d15 Diagnostic This code is simply showing you the current speed at which your boiler's internal air fan is spinning, rather than indicating a fault. d16 Diagnostic Your boiler has detected an issue with the sensor that monitors the temperature of the gases leaving your flue, causing it to stop operating to ensure safety. d17 Diagnostic Your boiler is simply displaying the current temperature of the water flowing through your heating system as part of its standard diagnostic readout. d18 Diagnostic Your boiler is currently running a special drying program designed for new underfloor heating systems, which will end automatically once the set time is reached. d19 Diagnostic Your boiler is displaying an internal software diagnostic screen, which usually means the system is performing a self-check or has encountered a minor glitch in its display settings. d22 Diagnostic Your boiler is reminding you that it is time for its annual safety service to ensure it continues to run efficiently and safely.
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