Alpha Eco Fault codes & diagnostics

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

Combi Natural Gas 24-28 kW 2006-2009 Discontinued

Replaced by: Eco2

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Severity at a glance

Each cell = one fault code. Hover to identify.
2 Emergency 19 High 3 Medium 1 Low

All 25 documented codes

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01

Your boiler is failing to light the internal flame, which means it cannot provide heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

02

Your boiler has detected that it is running too hot and has automatically shut down to prevent internal damage.

High Engineer only £120-250

Parts commonly replaced

  • Pump
  • NTC Sensor
  • Primary Heat Exchanger

Related codes

03

Your boiler has detected that the internal component responsible for clearing spent gases is not operating, so it has safely shut down to prevent unsafe operation.

High Engineer only £150-300

Parts commonly replaced

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

Related codes

04

Your boiler has detected a loose or faulty electrical connection to the internal gas control system, which prevents it from firing safely.

Emergency Engineer only £120-250

Parts commonly replaced

  • Gas valve wiring harness
  • Gas valve assembly
  • Main PCB

Related codes

05

Your boiler has lost the ability to accurately measure the temperature of the water being sent to your radiators, so it has shut down to prevent the system from overheating.

High Engineer only £120-200

Parts commonly replaced

  • NTC Sensor
  • Wiring harness

Related codes

06

Your boiler is struggling to accurately measure the temperature of your hot water, which means it has stopped providing it to prevent system errors.

Medium Engineer only £120-200

Parts commonly replaced

  • DHW NTC thermistor sensor
  • Wiring harness

Related codes

08

Your boiler has stopped because the water pressure inside the system has dropped too low or risen too high, preventing it from heating safely.

High DIY-safe £80-150

What to check first

  1. Check the pressure gauge on the front of the boiler; if it is below 1 bar, locate the metal filling loop underneath.
  2. Open the filling loop valves slowly to allow mains water into the system until the gauge reads between 1 and 1.5 bar.
  3. Close both valves tightly and restart the boiler.

Parts commonly replaced

  • Pressure Relief Valve
  • Pressure Transducer

Related codes

10

Your boiler has switched itself off because the water level inside the heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, usually a silver flexible hose with one or two valves attached to your boiler pipes.
  2. Open the valve(s) slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and restart the boiler.

Parts commonly replaced

  • Pressure gauge
  • Filling loop
  • Pressure sensor
12

Your boiler is struggling to accurately measure the temperature of your hot water cylinder because there is an issue with the sensor connection or the sensor itself.

Medium Engineer only £120-220

Parts commonly replaced

  • NTC Cylinder Sensor
  • Wiring Loom

Related codes

15

Your boiler's computer is struggling to read its own settings, which prevents it from starting up correctly.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
Showing 11–20 of 25
16

Your boiler has detected that the internal fan is moving too slowly or too fast, so it has shut down to prevent unsafe operation.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)

Related codes

20

Your boiler has detected a flame signal even though it is supposed to be switched off, which is a safety concern that prevents it from restarting.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)
  • Ionisation electrode
24

Your boiler's control panel is registering a button as being permanently pressed or stuck, which is preventing it from operating correctly.

High DIY-safe £120-200

What to check first

  1. Ensure no debris, dust, or moisture is trapped under the buttons of the control panel.
  2. Gently press and release each button on the interface several times to see if it frees a stuck mechanism.
  3. Turn the boiler off at the fused spur for 60 seconds to perform a hard reset, then turn it back on.

Parts commonly replaced

  • User Interface PCB
  • Control Panel Overlay
25

Your boiler is overheating because it cannot move the hot water away from the heating unit fast enough.

High Engineer only £150-250

Parts commonly replaced

  • Pump
  • Diverter valve
  • Primary heat exchanger

Related codes

27

Your boiler is struggling to pump water around your radiators, so it has turned itself off to prevent overheating.

High DIY-safe £120-250

What to check first

  1. Check that all radiator valves throughout the house are fully open
  2. Ensure the central heating system pressure is at the correct level, usually between 1 and 1.5 bar
  3. Bleed all radiators to ensure there is no trapped air preventing water flow

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve
29

Your boiler has detected that a temperature sensor in the exhaust system is sending incorrect information, so it has safely shut down to prevent damage.

High Engineer only £120-220

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness
31

Your boiler has lost its connection to its wall controller or thermostat, meaning it cannot receive signals to turn on your heating or hot water.

High DIY-safe £90-180

What to check first

  1. Check the batteries in your remote thermostat unit and replace them if necessary
  2. Turn the boiler off at the fused spur or mains power for 60 seconds, then turn it back on to reset the connection
  3. Check that the signal receiver box near the boiler is powered on and flashing correctly

Parts commonly replaced

  • Wireless receiver unit
  • PCB board
  • Communication cable
37

Your boiler has detected that the electricity supply coming into your home is weaker than it needs to be to run the system safely.

High Engineer only £120-250

Parts commonly replaced

  • PCB
  • Wiring harness
38

Your boiler has stopped because the internal flame has unexpectedly gone out while it was trying to heat your water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Flame sensor
  • Gas valve

Related codes

43

Your boiler is repeatedly struggling to keep its internal flame lit while trying to run.

High Engineer only £150-300

Parts commonly replaced

  • Flame rectification probe
  • Gas valve
  • Ignition electrode
Showing 21–25 of 25
46

Your boiler has lost the connection to an optional external temperature sensor, which usually means a wire has come loose or the sensor has been disconnected.

Low Engineer only £90-180

Parts commonly replaced

  • External weather compensation sensor
  • Wiring harness
47

Your boiler has detected that the exhaust gases are getting too hot and has automatically slowed down to protect itself from overheating.

High Engineer only £150-300

Parts commonly replaced

  • Flue thermostat
  • Primary heat exchanger
  • NTC sensor
51

Your boiler has lost its wireless connection to the heating controller, so it no longer knows when to switch on or off.

Medium DIY-safe £90-200

What to check first

  1. Check that the batteries in your wall-mounted thermostat are fresh and working
  2. Turn the power to the boiler off at the fused spur, wait 60 seconds, and turn it back on to reset the connection
  3. Ensure the wireless receiver unit near the boiler is not obstructed by large metal objects

Parts commonly replaced

  • Wireless RF receiver
  • Room thermostat unit
  • PCB
Overheat Thermostat operates

Your boiler has detected that it is getting too hot and has safely shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • Diverter valve
  • Heat exchanger
Pilot does not remain alight

Your boiler's small starter flame is failing to stay on, which prevents the main burner from igniting and stops your heating and hot water from working.

High Engineer only £120-250

Parts commonly replaced

  • Thermocouple
  • Pilot injector
  • Gas valve