Vokera Easi-Heat I Fault codes & diagnostics

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

Combi Natural Gas 25-29 kW 2022-present
GC Numbers 47-364-7147-364-72
Download the Vokera Easi-Heat I manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
3 Emergency 38 High 15 Medium 7 Low
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-364-71 EASI-HEAT i 25C 2022–present
47-364-72 EASI-HEAT i 29C 2022–present
Just want the most common Vokera Easi-Heat I faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 63 documented codes

Tap any card for details

>3.0 bar

Your boiler's internal water pressure is currently too high, which is causing the system to stop working to avoid potential damage.

High DIY-safe £80-150

What to check first

  1. Locate a radiator in your home, preferably one upstairs.
  2. Place a cloth and a bowl under the radiator bleed valve.
  3. Use a radiator key to open the valve slightly until water comes out, then close it once the pressure gauge on the boiler drops back to the 'green' zone (usually 1.0 to 1.5 bar).

Parts commonly replaced

  • Pressure Relief Valve (PRV)
  • Expansion Vessel
  • Filling Loop
Full explanation for >3.0 bar
04

Your boiler has failed to ignite or stay lit after several attempts and requires a manual reset and investigation by a professional.

High Engineer only £100-£250

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Electrode
  • Gas Valve
  • PCB

Related codes

Full explanation for 04
09

Your boiler has failed to fire up or complete its safety checks after several attempts and has now locked itself out for safety.

High DIY-safe £120-£350

What to check first

  1. Locate the mode selector switch on the front panel.
  2. Turn the switch to the 'OFF/RESET' position and wait for 10 seconds.
  3. Turn the switch back to either 'Hot Water Only' or 'Heating and Hot Water' to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 09
10

Your boiler is experiencing a temporary communication error or sensing issue that is preventing it from firing correctly.

Medium DIY-safe £100-280

What to check first

  1. Locate the mode selector switch on the front control panel.
  2. Turn the switch to the 'OFF/RESET' position and wait for 10 seconds.
  3. Turn the switch back to either 'Hot Water Only' or 'Heating and Hot Water' to restart the system.

Parts commonly replaced

  • Main PCB
  • Ignition NTC sensor
  • Wiring harness

Related codes

Full explanation for 10
12

Your boiler is attempting to restart its ignition process because it failed to light or maintain a flame.

High DIY-safe £100-350

What to check first

  1. Check if your gas supply is turned on and other gas appliances are working
  2. Press the reset button or turn the selector switch to 'OFF/RESET' for several seconds
  3. Ensure the condensate pipe (the white plastic pipe outside) isn't frozen if it is winter

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 12
13

Your boiler has detected an electrical communication problem within its internal wiring which is preventing it from running safely.

High Engineer only £120-280

Parts commonly replaced

  • Wiring harness
  • Main PCB
  • Control board connectors

Related codes

Full explanation for 13
13/14

Your boiler has detected an issue with the internal electrical connections that prevents it from operating safely.

High Engineer only £120-250

Parts commonly replaced

  • Wiring harness
  • PCB (Printed Circuit Board)
  • Sensor connections

Related codes

Full explanation for 13/14
14

Your boiler has detected an internal communication problem between its electronic components and is unable to fire up.

High Engineer only £100-280

Parts commonly replaced

  • Wiring Harness
  • Main Control Board (PCB)

Related codes

Full explanation for 14
15

Your boiler thinks it sees a flame even though it hasn't started the ignition process yet, which is causing it to shut down for safety.

High Engineer only £120-280

Parts commonly replaced

  • Ionisation Probe
  • Printed Circuit Board (PCB)
  • Gas Valve

Related codes

Full explanation for 15
20

Your boiler has identified a temporary electronic error and is likely trying to restart itself automatically.

Low DIY-safe £80-160

What to check first

  1. Check if the boiler clears the code and restarts automatically after a few minutes
  2. Turn the mode selector switch to the 'OFF/RESET' position, wait five seconds, then turn it back to 'ON'
  3. Ensure your gas supply is active (e.g. check other gas appliances)

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Ignition Electrode

Related codes

Full explanation for 20
Showing 11–20 of 63
21

Your boiler has lost communication with its external controls or is stuck in an internal testing phase, meaning it cannot start the heating cycle.

High DIY-safe £100-280

What to check first

  1. Locate the selector switch on the front panel
  2. Turn the dial to the 'OFF/RESET' position and wait for 10 seconds
  3. Turn the dial back to the 'Hot Water' or 'Heating and Hot Water' position

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • External Timeclock
  • Wiring Harness

Related codes

Full explanation for 21
23

Your boiler has detected an internal communication problem between its electronic components or a possible electrical connection fault.

High Engineer only £120-350

Parts commonly replaced

  • Wiring harness
  • Printed Circuit Board (PCB)
  • Internal sensors

Related codes

Full explanation for 23
24

Your boiler has detected an internal communication glitch or a temporary sensor error that it is currently trying to rectify automatically.

Medium DIY-safe £100-250

What to check first

  1. Observe the boiler to see if the code clears automatically
  2. Press the reset button if the fault becomes permanent
  3. Monitor the boiler for frequent recurrences of this code
  4. Contact a qualified engineer if the fault persists after a reset

Parts commonly replaced

  • Main PCB (Control Board)
  • Wiring Loom

Related codes

Full explanation for 24
25

Your boiler has detected a temporary internal communication error or a logic conflict and is likely attempting a self-correction or restart.

Low DIY-safe £0-120

What to check first

  1. Turn the boiler mode selector switch to the 'OFF/RESET' position.
  2. Wait for approximately 10 seconds.
  3. Turn the switch back to either the 'Heating & Hot Water' or 'Hot Water Only' position.

Parts commonly replaced

  • None (usually software reset)
  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 25
26

Your boiler is experiencing a temporary communication error or internal glitch that usually resolves itself, but may require a simple reset if the heating doesn't resume.

Medium DIY-safe £0-120

What to check first

  1. Check if the boiler clears the code automatically after a few minutes
  2. Press the reset button once to clear the temporary fault
  3. Monitor the boiler for recurring instances of this code

Parts commonly replaced

  • No parts usually required
  • Main PCB

Related codes

Full explanation for 26
27

Your boiler has detected an internal electronic communication error or a temporary sensor discrepancy and has paused operation for safety.

Medium DIY-safe £120-280

What to check first

  1. Turn the mode selector knob to the 'OFF/RESET' position.
  2. Wait for 30 seconds.
  3. Turn the knob back to the 'ON' or 'Winter' position to see if the error clears.

Parts commonly replaced

  • Main PCB (Control Board)
  • Thermistor (NTC Sensor)

Related codes

Full explanation for 27
28

Your boiler has detected a temporary internal communication error and is attempting to restart itself.

Medium DIY-safe £0-120

What to check first

  1. Wait up to 15 minutes for the boiler to complete its automatic restart sequence
  2. If the code remains, turn the mode selector switch to the 'OFF/RESET' position
  3. Wait 10 seconds, then return the switch to the 'ON' or 'WINTER' position
  4. Ensure any external controls or thermostats are calling for heat

Parts commonly replaced

  • No parts usually required
  • Main PCB (if fault persists)

Related codes

Full explanation for 28
29

Your boiler has detected an issue with the air pressure or flue gases and is currently waiting for the condition to clear before attempting to restart.

Medium Engineer only £120-280

Parts commonly replaced

  • Air pressure switch
  • Fan
  • Flue venturi
  • Main PCB

Related codes

Full explanation for 29
30

Your boiler has detected a temporary internal communication error or a potential problem with the fan or air supply that may reset itself or require a manual restart.

Medium DIY-safe £120-280

What to check first

  1. Locate the mode selector switch on the front control panel.
  2. Turn the switch to the 'OFF/RESET' position and wait for 10 seconds.
  3. Turn the switch back to the 'ON' position (heating or hot water) to see if the code clears.

Parts commonly replaced

  • Fan
  • Air Pressure Switch
  • Main PCB

Related codes

Full explanation for 30
31

Your boiler is experiencing a communication or configuration error between internal electronic boards that prevents it from starting correctly.

High Engineer only £140-£350

Parts commonly replaced

  • Main PCB
  • Display Interface Board
  • Wiring Harness

Related codes

Full explanation for 31
Showing 21–30 of 63
32

Your boiler has stopped working because the internal fan, which safely exhausts gases out of the flue, is not spinning at the correct speed or has failed completely.

High Engineer only £200-£450

Parts commonly replaced

  • Fan assembly
  • Main circuit board (PCB)
  • Fan wiring harness

Related codes

Full explanation for 32
34

Your boiler has detected an unusual fan speed or air flow issue but is attempting to reset itself automatically.

Medium Engineer only £120-280

Parts commonly replaced

  • Fan assembly
  • Venture tube
  • Air pressure switch

Related codes

Full explanation for 34
35

Your boiler has stopped working because the internal fan, which safely clears exhaust gases, isn't spinning or communicating correctly with the system.

High Engineer only £180-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

Full explanation for 35
36

Your boiler's main internal computer has detected a technical error and has stopped working to protect the system.

High Engineer only £250-£450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Control Board

Related codes

Full explanation for 36
37

Your boiler has detected that the internal fan is spinning too fast, which is preventing the system from starting safely.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 37
38

Your boiler’s internal computer has lost its programmed settings and no longer knows how to operate correctly.

High Engineer only £100-350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Control Knob set

Related codes

Full explanation for 38
40

Your boiler has detected a temporary internal communication or sensor timing error and is essentially waiting to see if it clears itself.

Medium DIY-safe £80-180

What to check first

  1. Monitor the boiler to see if the code clears automatically
  2. Press the reset button if the code remains or turns into a lockout
  3. Ensure power to the boiler has not been interrupted or fluctuated

Parts commonly replaced

  • Flow thermistor (NTC)
  • Main PCB

Related codes

Full explanation for 40
41

Your boiler has detected a temporary internal communication issue or a potential sensor error and is trying to reset itself.

Low DIY-safe £0-120

What to check first

  1. Turn the control knob to the 'OFF/RESET' position.
  2. Wait for approximately 30 seconds.
  3. Turn the knob back to your desired 'Heating' or 'Hot Water' setting.

Parts commonly replaced

  • Temperature sensor (NTC thermistor)
  • Wiring harness

Related codes

Full explanation for 41
42

Your boiler has detected a temporary internal communication or sensor error that may resolve itself or lead to a full lockout.

Medium DIY-safe £100-220

What to check first

  1. Check if the boiler is in a lockout state
  2. Perform a system reset by turning the selector switch to the reset position and back
  3. Monitor the boiler to see if the code recurs or becomes a permanent fault
  4. Ensure the system pressure is within the normal operating range (usually 1.0 to 1.5 bar)

Parts commonly replaced

  • Temperature thermistor (NTC)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 42
50

Your boiler's internal computer has encountered a memory or software error that prevents it from running safely.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Control Knob Potentiometers

Related codes

Full explanation for 50
Showing 31–40 of 63
52

Your boiler's internal computer has encountered a memory or software error that prevents it from running safely.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Control Knob Potentiometers

Related codes

Full explanation for 52
53

Your boiler's electronic control board has detected an internal computer error and has shut down as a safety precaution.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 53
56

Your boiler's electronic control board has detected an internal computer error and has shut down as a safety precaution.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 56
60

Your boiler is experiencing a temporary communication error or a sensor timing issue that is causing it to pause current operations.

Medium DIY-safe £100-250

What to check first

  1. Press the reset button on the front control panel
  2. Turn the selector switch to the 'OFF/RESET' position and then back to 'ON'
  3. Monitor the boiler to see if the error code clears and operation resumes

Parts commonly replaced

  • Thermistor (NTC Sensor)
  • Main Control Board

Related codes

Full explanation for 60
70

Your boiler has detected a temporary technical issue that frequently relates to an internal communication error or a sensor detecting an unusual reading.

High DIY-safe £100-280

What to check first

  1. Locate the mode selector switch on the front panel
  2. Turn the switch to the 'OFF/RESET' position
  3. Wait for 30 seconds
  4. Move the switch back to the 'ON' (winter or summer) position

Parts commonly replaced

  • Main PCB (Control Board)
  • Thermistor

Related codes

Full explanation for 70
71

Your boiler has detected an internal communication or temperature sensor error that is currently preventing it from running normally.

High DIY-safe £120-280

What to check first

  1. Turn the mode selector switch to the 'OFF/RESET' position.
  2. Wait for approximately 30 seconds.
  3. Turn the switch back to the 'ON' or heating/hot water position.

Parts commonly replaced

  • NTC Temperature Sensor
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 71
72

Your boiler has detected a temporary sensor problem or an unusual temperature difference, which may cause the system to pause or restart.

Medium DIY-safe £80-160

What to check first

  1. Check if the boiler display resets itself automatically after a short period
  2. Press the reset button or turn the mode selector switch to 'OFF/RESET' and then back to heating/hot water
  3. Ensure your system pressure is topped up to between 1 and 1.5 bar on the pressure gauge

Parts commonly replaced

  • NTC Temperature Sensor
  • Primary Heat Exchanger (cleaning)

Related codes

Full explanation for 72
74

Your boiler is unable to move water around the system because either the main pump is stuck or the internal valves are blocked.

High Engineer only £180-350

Parts commonly replaced

  • Circulation pump
  • Diverter valve
  • Flow switch

Related codes

Full explanation for 74
75

Your boiler has detected an internal electrical communication error or a wiring issue that is preventing it from working safely.

High Engineer only £100-£350

Parts commonly replaced

  • Wiring harness
  • Main PCB
  • Ignition transformer

Related codes

Full explanation for 75
78

Your boiler has detected a temporary internal communication error or a sensor synchronization issue that is preventing it from running properly.

High DIY-safe £100-280

What to check first

  1. Turn the selector switch to the 'OFF/RESET' position.
  2. Wait for approximately 30 seconds.
  3. Turn the selector switch back to the 'ON' position (Heating and Hot Water icon).

Parts commonly replaced

  • Domestic Hot Water (DHW) Thermistor
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 78
Showing 41–50 of 63
79

Your boiler has detected an internal communication error or a temporary processing fault that is preventing it from running properly.

High DIY-safe £150-350

What to check first

  1. Locate the mode selector switch on the front panel
  2. Turn the switch to the 'OFF/RESET' position and wait for 10 seconds
  3. Turn the switch back to either 'Hot Water Only' or 'Heating and Hot Water' to see if the error clears

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for 79
80

Your boiler is experiencing a temporary communication error or initialization issue that may prevent it from starting correctly.

Medium DIY-safe £100-220

What to check first

  1. Locate the mode selector switch on the front of the boiler.
  2. Turn the switch to the 'OFF/RESET' position and wait for 5 seconds.
  3. Turn the switch back to either 'Hot Water Only' or 'Heating and Hot Water' to restart the system.

Parts commonly replaced

  • Main Control PCB
  • Wiring harness

Related codes

Full explanation for 80
90

Your boiler has paused operation due to a temporary internal communication or sensor error that may clear itself or indicate a service is needed.

Low DIY-safe £0-120

What to check first

  1. Turn the selector switch to the 'OFF/RESET' position.
  2. Wait approximately 30 seconds.
  3. Turn the selector switch back to either the 'Heating' or 'Hot Water' position.

Parts commonly replaced

  • NTC Temperature Sensor
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 90
92

Your boiler has detected a temporary internal error and is attempting to self-correct or reset after a specific cycle.

Medium DIY-safe £0-80

What to check first

  1. Wait for the boiler to complete its internal self-test cycle
  2. Press the reset button if the code remains after 10 minutes
  3. Monitor the boiler for recurring faults
  4. Ensure power to the boiler is stable and not switched off prematurely

Parts commonly replaced

  • None (Software reset)
  • Main PCB (if code persists)

Related codes

Full explanation for 92
93

Your boiler is experiencing a temporary communication or sensor error that may resolve itself but often indicates a part is beginning to fail.

Medium DIY-safe £100-280

What to check first

  1. Press the reset button to clear the temporary error
  2. Monitor the boiler for recurring faults
  3. Ensure power supply to the boiler is stable
  4. Contact a Gas Safe engineer if the code persists

Parts commonly replaced

  • Main PCB
  • NTC Sensor
  • Wiring loom

Related codes

Full explanation for 93
94

Your boiler has detected a minor internal communication error and and is currently attempting to automatically reset itself.

Low DIY-safe £0-120

What to check first

  1. Wait up to 10 minutes to see if the boiler clears the code automatically
  2. Turn the mode selector switch to the 'OFF/RESET' position and then back to 'ON'
  3. Check if the display returns to the standard temperature output

Parts commonly replaced

  • None (Software reset)
  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 94
95

Your boiler has detected a temporary internal communication or processing error and is attempting to resolve itself.

Low DIY-safe £0-120

What to check first

  1. Wait for the boiler to complete its current operation and reset the code automatically
  2. Turn the mode selector knob to the 'OFF/RESET' position and then back to 'ON'
  3. Ensure there is a constant power supply to the unit without frequent switching

Parts commonly replaced

  • None (Software reset)
  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 95
A10

Your boiler has stopped working because it cannot safely get rid of exhaust gases or water produced during the heating process, triggering a safety shutdown.

Emergency Engineer only £120-250

Parts commonly replaced

  • Condensate trap
  • Flue seal
  • Air pressure switch
  • Fan
Full explanation for A10
A11

Your boiler is unable to drain away the water it produces during normal operation, causing it to shut down to prevent internal damage.

High Engineer only £90-180

Parts commonly replaced

  • Condensate trap
  • Condensate pipework

Related codes

Full explanation for A11
A20

Your boiler is struggling to breathe because the pipe that vents exhaust gases outside or draws in fresh air is blocked or damaged.

Emergency Engineer only £120-250

Parts commonly replaced

  • Flue assembly
  • Fan unit
  • Air pressure switch

Related codes

Full explanation for A20
Showing 51–60 of 63
A30

Your boiler has detected a flame inside when it should be turned off, which means the system is not shutting down correctly and needs professional attention.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for A30
A40

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

High Engineer only £120-220

Parts commonly replaced

  • Limit thermostat
  • Pump
  • Diverter valve
  • Primary heat exchanger

Related codes

Full explanation for A40
A41

Your boiler has stopped working because the water pressure inside your heating system has dropped too low.

High DIY-safe £0-£150

What to check first

  1. Locate the filling loop (a silver flexi-hose) underneath the boiler.
  2. Open the valves on both ends of the filling loop to allow water to enter the system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches between 1.0 and 1.5 bar.
  4. Close both valves tightly and remove the filling loop if required.

Parts commonly replaced

  • Pressure relief valve
  • Pressure sensor
  • Expansion vessel
Full explanation for A41
A42

Your boiler has stopped because the water pressure inside the system is too low.

High DIY-safe £0 (DIY fix) or £80-120 (professional callout)

What to check first

  1. Locate the external filling loop, which is usually a flexible silver braided hose under the boiler.
  2. Open the two valves on either end of the hose to allow water into the system until the gauge on the boiler front reads between 1 and 1.5 bar.
  3. Close both valves tightly and restart the boiler.

Parts commonly replaced

  • Filling loop
  • Pressure gauge
  • Pressure relief valve

Related codes

Full explanation for A42
A58

Your boiler is struggling to accurately read the temperature of the water returning to it, which causes it to stop working to prevent potential overheating.

High Engineer only £120-200

Parts commonly replaced

  • Return NTC sensor
  • Wiring harness

Related codes

Full explanation for A58
A59

Your boiler has detected that the water returning to it is much hotter than it should be, causing the system to shut down for safety.

High Engineer only £120-250

Parts commonly replaced

  • Return NTC sensor
  • Pump
  • PCB

Related codes

Full explanation for A59
A60

Your boiler is currently unable to read its internal water pressure correctly, so it has shut itself down as a precaution to prevent damage.

High Engineer only £150-250

Parts commonly replaced

  • Pressure transducer
  • Wiring harness

Related codes

Full explanation for A60
A70

Your boiler is struggling to accurately measure the temperature of your hot water, which means it will likely stop providing hot water to your taps until the faulty sensor is replaced.

High Engineer only £120-200

Parts commonly replaced

  • DHW NTC sensor
  • Wiring harness

Related codes

Full explanation for A70
A80

Your boiler has detected that the water returning to it is too hot or that the internal temperature sensors are receiving conflicting information, causing it to shut down for safety.

High Engineer only £150-250

Parts commonly replaced

  • Return NTC thermistor
  • Wiring harness
  • PCB
Full explanation for A80
A90

Your boiler has detected that the water inside the system is getting much hotter than it should be, so it has shut itself down to prevent damage.

High Engineer only £150-250

Parts commonly replaced

  • NTC sensor
  • Primary heat exchanger
  • Pump

Related codes

Full explanation for A90
Showing 61–63 of 63
A91

Your boiler has detected that the water temperature is behaving unexpectedly, suggesting a potential circulation issue or a faulty temperature reading.

High Engineer only £120-250

Parts commonly replaced

  • NTC Temperature Sensors
  • Circulation Pump
  • Primary Heat Exchanger

Related codes

Full explanation for A91
FIL

Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.

High DIY-safe £0-£100

What to check first

  1. Locate the external filling loop, which is usually a small metal braided hose connected to your boiler pipes.
  2. Open the small valve(s) on the loop to allow mains water into the heating system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically between 1.0 and 1.5 bar).
  4. Close the valve(s) tightly and check that the pressure remains steady.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure gauge
Full explanation for FIL
SFS

Your boiler has reached its programmed service interval limit and is simply reminding you that it is time for a professional maintenance check.

Low Engineer only £90-130
Full explanation for SFS
Status & diagnostic codes

4 operating states & engineer diagnostics

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

AF1 Status Your boiler has detected that the temperature is dropping very low and has activated its internal frost protection mode to prevent the water inside from freezing. AF2 Status Your boiler has detected that the water inside the pipes used for your taps and shower is getting too cold and has activated a protection mode to prevent them from freezing. CFS Diagnostic Your boiler has detected an internal issue that requires a qualified engineer to investigate and perform a mandatory safety check. E091 Diagnostic Your boiler has detected that the internal part responsible for transferring heat has become clogged with debris or scale and needs professional cleaning to work efficiently.
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