BoilerFaultCodes A0
Your boiler is displaying a memory code that indicates a previous fault has occurred in the past, but it does not necessarily mean the boiler is currently broken.
Sime Metropolis DGT 25 BF Fault codes & diagnostics
19 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 2008-2016 Discontinued
GC Number 47-283-22
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Severity at a glance
Each cell = one fault code. Hover to identify. 8 High
7 Medium
4 Low
Just want the most common Sime Metropolis DGT 25 BF faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 19 documented codes
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A1 Your boiler is displaying a memory code that indicates a previous fault occurred, but it does not specify what that fault was or if it is currently happening.
Your boiler is displaying a memory code that indicates a previous fault occurred, but it does not specify what that fault was or if it is currently happening.
Related codes
A2 Your boiler has recorded a fault in its memory that requires a professional to investigate the underlying cause.
Your boiler has recorded a fault in its memory that requires a professional to investigate the underlying cause.
Parts commonly replaced
- PCB
- Wiring harness
- NTC sensors
Related codes
A3 Your boiler has recorded a historical technical error that suggests the system has encountered a communication or sensor fault in the past.
Your boiler has recorded a historical technical error that suggests the system has encountered a communication or sensor fault in the past.
Parts commonly replaced
- Main PCB
- Wiring harness
- Temperature sensor
Related codes
A4 Your boiler is displaying a memory code indicating that it previously encountered a fault and shut down for safety reasons, though it may currently be working.
Your boiler is displaying a memory code indicating that it previously encountered a fault and shut down for safety reasons, though it may currently be working.
Parts commonly replaced
- Control PCB
- Wiring harness
Related codes
A5 Your boiler has recorded a historical memory error, which usually means the system is logging a past fault that needs to be cleared by a professional.
Your boiler has recorded a historical memory error, which usually means the system is logging a past fault that needs to be cleared by a professional.
Parts commonly replaced
- Main PCB
- Control board
Related codes
A6 Your boiler has recorded a fault in its history that indicates the fan or flue system failed to operate correctly during a previous cycle.
Your boiler has recorded a fault in its history that indicates the fan or flue system failed to operate correctly during a previous cycle.
Parts commonly replaced
- Fan unit
- Air pressure switch
- Flue seals
- PCB
Related codes
A7 Your boiler has recorded an internal memory error, which is often a sign of a temporary glitch that might resolve itself or a deeper issue with the boiler's main brain.
Your boiler has recorded an internal memory error, which is often a sign of a temporary glitch that might resolve itself or a deeper issue with the boiler's main brain.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
A8 Your boiler has recorded a fault in its memory history, but this code specifically identifies that there is no active error currently preventing the unit from operating.
Your boiler has recorded a fault in its memory history, but this code specifically identifies that there is no active error currently preventing the unit from operating.
Related codes
A9 Your boiler has recorded a previous error that has now been cleared or is currently blocked, preventing it from functioning correctly.
Your boiler has recorded a previous error that has now been cleared or is currently blocked, preventing it from functioning correctly.
Parts commonly replaced
- Control board
- Temperature sensor
Related codes
AL 02 Your boiler has stopped working because the water pressure is too low and it needs to be topped up.
Your boiler has stopped working because the water pressure is too low and it needs to be topped up.
What to check first
- Locate the filling loop (usually a silver braided hose with small valves) underneath the boiler.
- Slowly open the valves one at a time until you hear water flowing.
- Watch the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.2 bar, then close both valves tightly.
Parts commonly replaced
- Filling loop
- Pressure sensor
- Expansion vessel
Related codes
AL 04 Your boiler's hot water sensor has failed or has a bad connection, which means the system cannot correctly measure the temperature of the water coming out of your taps.
Your boiler's hot water sensor has failed or has a bad connection, which means the system cannot correctly measure the temperature of the water coming out of your taps.
Parts commonly replaced
- Domestic Hot Water (DHW) NTC Sensor
- Wiring Harness
Related codes
AL 05 Your boiler has detected a fault with the internal temperature sensor that monitors heat being sent to your taps or radiators, preventing the system from heating up.
Your boiler has detected a fault with the internal temperature sensor that monitors heat being sent to your taps or radiators, preventing the system from heating up.
Parts commonly replaced
- NTC Temperature Sensor
- Wiring Harness
Related codes
AL 06 Your boiler has tried to light but cannot detect a flame, meaning it won't produce any heat or hot water.
Your boiler has tried to light but cannot detect a flame, meaning it won't produce any heat or hot water.
What to check first
- Check if other gas appliances (like a hob) are working to ensure gas is reaching your home.
- Verify that your gas prepaid meter hasn't run out of credit.
- Press the 'Reset' button on the boiler control panel once to see if the system restarts.
Parts commonly replaced
- Ignition electrode
- Flame detection probe
- Gas valve
Related codes
AL 07 Your boiler has switched itself off because it has detected that the water inside the unit is getting too hot.
Your boiler has switched itself off because it has detected that the water inside the unit is getting too hot.
What to check first
- Check that your radiator valves are open and not turned off.
- Verify that your system water pressure is between 1 and 1.5 bar on the gauge.
- Try to reset the boiler by turning the selector dial to the 'OFF/RESET' position and then back to 'ON'.
Parts commonly replaced
- Overheat Thermostat
- Temperature Sensor (NTC)
- Circulation Pump
Related codes
AL 08 Your boiler is failing to detect a flame, which means it cannot fire up to provide heating or hot water.
Your boiler is failing to detect a flame, which means it cannot fire up to provide heating or hot water.
What to check first
- Check that your gas emergency control valve is open and other gas appliances are working.
- Reset the boiler by turning the selector switch to the 'R' position for a few seconds.
- Verify if your pre-paid gas meter has credit, if applicable.
Parts commonly replaced
- Ignition electrode
- Detection electrode
- Gas valve
- Printed Circuit Board (PCB)
Related codes
AL 11 Your boiler is unable to control the gas flow properly because a vital internal electrical connection has been lost, causing the system to shut down for safety.
Your boiler is unable to control the gas flow properly because a vital internal electrical connection has been lost, causing the system to shut down for safety.
Parts commonly replaced
- Gas Valve Modulator
- Wiring Harness
- Main PCB
Related codes
AL 12 Your boiler's computer is confused about which type of ventilation it has and needs its settings updated to restart correctly.
Your boiler's computer is confused about which type of ventilation it has and needs its settings updated to restart correctly.
Parts commonly replaced
- Main PCB (if settings will not save)
Related codes
AL 17 Your boiler has detected that its two internal temperature sensors are giving very different readings, causing it to shut down for safety.
Your boiler has detected that its two internal temperature sensors are giving very different readings, causing it to shut down for safety.
Parts commonly replaced
- NTC heating sensors
- Dual sensor probe
- Main PCB
Related codes
Status & diagnostic codes 31 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
31 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
01 Diagnostic Your boiler has failed to ignite or stay lit, meaning it cannot produce heat or hot water until the issue is addressed. 02 Diagnostic Your boiler is struggling to detect water movement or pressure, which prevents it from safely heating your home. 03 Diagnostic Your boiler has detected an issue with its internal power supply or control board, causing it to shut down for safety. 04 Diagnostic Your boiler is struggling to read the outdoor temperature correctly, which may lead to your heating running less efficiently than usual. 05 Diagnostic The boiler control buttons have become unresponsive, likely due to a software lock or a faulty display interface preventing you from changing settings. 10 Diagnostic Your boiler is currently running its built-in protection cycle to prevent the internal water from freezing, which is normal behavior during very cold weather. 11 Diagnostic Your boiler has detected that the outdoor temperature sensor is reporting an extremely low reading, causing the system to run in a protective mode to prevent pipes from freezing. 12 Diagnostic Your boiler is signalling that the external weather-responsive settings are not configured or are inconsistent, which may result in your heating not adjusting correctly to the outside temperature. 13 Diagnostic Your boiler has detected that the water inside the system is failing to reach the minimum temperature required to operate safely. 14 Diagnostic Your boiler has detected that the water inside the heating system is getting dangerously hot and has shut itself down to prevent damage. 15 Diagnostic Your boiler is currently running at its maximum heating capacity, which is a status message rather than a breakdown. 16 Diagnostic Your boiler is currently running a mandatory cooling cycle to move excess heat away from the internal components after a period of activity. 17 Diagnostic Your boiler is momentarily pausing the flow of water to the radiators, likely because it is detecting an issue with the pump that pushes the water around your system. 18 Diagnostic Your boiler is temporarily preventing itself from restarting because it has detected a recurring issue that needs a short pause before it tries to fire up again. 19 Diagnostic Your boiler is struggling to accurately measure the flow of hot water, which may cause your taps to run cold or the water temperature to fluctuate significantly. 29 Diagnostic Your boiler is currently performing a scheduled safety cycle to heat the water in its storage tank to a high temperature to kill potential bacteria. 49 Diagnostic Your boiler's computer memory has been wiped or corrupted, meaning it has lost the specific settings required to operate your heating system correctly. c0 Diagnostic This code is simply an information display showing the total number of hours your boiler's burner has been running, rather than an indication of a fault. c1 Diagnostic This code is simply an information display showing how many times your boiler has successfully lit, rather than an indication of a fault. c2 Diagnostic This code is simply an information display showing the total number of historical faults recorded by your boiler and does not indicate an active problem. c3 Diagnostic Your boiler's electronic control system is showing an error because its internal settings have become corrupted or are not properly configured. c4 Diagnostic Your boiler's computer is experiencing a software or configuration error that prevents it from operating correctly. i0 Diagnostic Your boiler is struggling to read the temperature from the outdoor sensor, which tells the system how hard to work based on the weather. i1 Diagnostic Your boiler has stopped working because it cannot correctly read the temperature of the water being sent to your radiators. i2 Diagnostic Your boiler has stopped heating your radiators because it is unable to accurately read the current water temperature inside the system. i3 Diagnostic Your boiler is struggling to detect the temperature of the water used for your taps and shower, which will likely prevent it from providing hot water. i4 Diagnostic Your boiler has detected a communication error with an external temperature sensor, which may prevent it from operating correctly or heating your home. i5 Diagnostic Your boiler is currently displaying a status code that indicates it is in the process of calibrating or reporting its internal heating temperature settings. i6 Diagnostic Your boiler has detected that it cannot maintain a stable flame, so it has safely shut itself down to prevent any issues. i7 Diagnostic Your boiler is having trouble managing the gas flame intensity, which means it has safely shut down to prevent inefficient or improper combustion. i8 Diagnostic Your boiler is failing to detect that you have turned on a hot tap, meaning it won't fire up to heat your water.