BoilerFaultCodes Communication fault
No communication with the PCB Communication fault between display and PCB in the electronics box
Vaillant ecoTEC plus 612 Fault codes & diagnostics
50 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
System Gas 2012 onwards Discontinued
GC Number 41-044-60
Download the Vaillant ecoTEC plus 612 manual
PDF
Versions & GC numbers
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. 2 Emergency
2 High
1 Medium
45 Unrated
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 |
|---|---|---|
| 41-044-60 | ecoTEC plus 612 VU GB 126/5-5 | 2012–2015 |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Vaillant ecoTEC plus 612 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 50 documented codes
Tap any card for details
F.00
Fault list
F.01
Return temperature sensor interruption
F.02
Interruption cylinder charging sensor actoSTOR (NTC) only in combination with F.91
F.03
Interruption cylinder sensor actoSTOR (NTC) only in combination with F.91
F.10
Flow NTC short circuit
F.11
Return NTC short circuit
F.12
Short circuit at cylinder charging sensor (NTC) only in combination with F.91
F.13
VU-/VUW boiler: Short circuit warm start sensor/cylinder sensor; VUW boiler with actoSTOR: Short circuit cylinder sensor (NTC) only in combination with F.91
F.20
Safety switch-off: temperature limiter
Showing 11–20 of 50
F.22
Low water pressure; the boiler switches off
F.23
Safety switch-off: Temperature difference too great
F.24
Safety switch-off: Temperature rise too fast
F.25
Safety switch-off: Flue gas temperature too high
F.26
Fault: Gas valve without function
F.27
Safety switch-off: Flame simulation
F.28
Failure during start-up: ignition unsuccessful
F.29 Your boiler was working but has suddenly turned off because the flame has gone out and it cannot manage to relight itself.
Your boiler was working but has suddenly turned off because the flame has gone out and it cannot manage to relight itself.
What to check first
- Check if other gas appliances, like a hob, are still working to ensure your gas supply hasn't been interrupted.
- If it is freezing outside, check the condensate pipe (the plastic pipe leading outside) for ice and defrost it with warm water.
- Press the reset button (a flame symbol with a cross through it) for five seconds to see if the boiler restarts.
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Flame Sensing Electrode
- PCB
Related codes
F.32
Fan fault
F.35
Air/flue gas duct fault
Showing 21–30 of 50
F.42
Coding resistor fault (possible in combination with F.70)
F.49
eBUS fault
F.52
Mass flow sensor connection fault
F.53 Your boiler has detected an issue with the gas flow, meaning it cannot safely ignite or maintain a flame to heat your home.
Your boiler has detected an issue with the gas flow, meaning it cannot safely ignite or maintain a flame to heat your home.
Parts commonly replaced
- Gas valve
- Gas valve wiring harness
- Main PCB
Related codes
F.54
Gas pressure fault (in combination with F.28/F.29)
F.56
Fault: Mass flow sensor regulation
F.57
Fault during comfort safety mode
F.61
Fault: Gas valve regulation - Short circuit/short to earth in cable harness for the gas valve - Gas valve defective (coils shorted to earth) - Electronics defective
F.62
Fault: Gas valve switch-off delay - Delayed shutdown of gas valve - Delayed extinguishing of flame signal - Gas valve leaking - Electronics defective
F.63
EEPROM error Electronics defective
Showing 31–40 of 50
F.64
Electronics/NTC fault Supply or return NTC short circuited, electronics defective
F.65
Electronic temperature fault Electronics overheating due to external influences, electronics defective
F.67
Electronics/flame fault Implausible flame signal, electronics defective
F.68
Unstable flame signal fault Air in gas, gas flow pressure too low, wrong air ratio, condensate route blocked, wrong gas restrictor, ionisation flow interruption (cables, electrodes), flue gas recirculation, condensate route
F.70
Coding resistor fault (possible in combination with F.42)
F.71
Flow NTC fault Flow temperature sensor signalling constant value: - Flow temperature sensor incorrectly positioned at supply pipe. - Flow temperature sensor defective.
F.72
Flow/return NTC fault Flow/return NTC temperature difference too great -> flow and/or return temperature sensor defective
F.73
Water pressure sensor signal in the wrong range (too low) Interruption/short circuit of water pressure sensor, interruption/short circuit to GND in supply line to water pressure sensor or water pressure sensor defective
F.74
Water pressure sensor signal outside correct range (too high) Cable to water pressure sensor has short-circuited at 5 V/24 V or internal fault in water pressure sensor
F.75
Interruption Flow Fehler Pumpe/Wassermangel
Showing 41–50 of 50
F.76
Overheating protection on primary heat exchanger has responded Cable or cable connections for safety fuse in primary heat exchanger or primary heat exchanger defective
F.77
Flue non-return flap/condensate pump fault No response from flue non-return flap or condensate pump defective
F.78
Interruption to DHW outlet sensor at external controller UK link box is connected, but hot water NTC not bridged
F.83
Flow and/or return temperature sensor temperature change fault When the burner starts, the temperature change registered at flow and/or return temperature sensor is non-existent or too small. - Not enough water in the boiler - Flow and/return temperature sensor not in correct position at pipe.
F.84
Fault: Flow/return temperature sensor temperature difference implausible Flow and return temperature sensors returning implausible values. - Flow and return temperature sensors have been inverted. - Flow and return temperature sensors have not been correctly fitted.
F.85
Fault: Flow and return temperature sensors incorrectly fitted Flow and/or return temperature sensors have been fitted to the same pipe/wrong pipe.
F.91 Your boiler is having trouble communicating with the separate hot water storage tank, which may result in a loss of hot water.
Your boiler is having trouble communicating with the separate hot water storage tank, which may result in a loss of hot water.
Parts commonly replaced
- actoSTOR sensor
- Wiring harness
- PCB
Related codes
F.92 Your boiler has detected an issue with the type of gas it is receiving, meaning it has shut itself down to prevent unsafe operation.
Your boiler has detected an issue with the type of gas it is receiving, meaning it has shut itself down to prevent unsafe operation.
Parts commonly replaced
- Gas valve
- Printed Circuit Board (PCB)
- Gas supply pressure regulator
Related codes
F.93 Your boiler has detected an issue with the gas valve or the way it is communicating, meaning it cannot safely start up to provide heat or hot water.
Your boiler has detected an issue with the gas valve or the way it is communicating, meaning it cannot safely start up to provide heat or hot water.
Parts commonly replaced
- Gas valve
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
S.24
DHW mode Burner on
Status & diagnostic codes 71 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
71 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
D.000 Diagnostic This code is simply a status message showing the boiler is currently operating at a reduced capacity, not a fault requiring any action. D.001 Diagnostic Your boiler is currently cooling down by circulating water through the system after the heating has switched off, which is a normal part of the shutdown process. D.002 Diagnostic Your boiler is currently in a waiting period between heating cycles to prevent it from switching on and off too frequently, which is a normal protective feature. D.003 Diagnostic Your boiler is simply reporting the current temperature of the water flowing out of it, which is a normal status reading rather than an active fault. D.004 Diagnostic Your boiler is struggling to accurately read or detect the current temperature of your hot water cylinder. D.005 Diagnostic Your boiler is simply reporting the current temperature target for the water circulating through your radiators, rather than indicating a fault. D.006 Diagnostic This code indicates that the boiler is simply reporting the temperature it is currently aiming to reach for your heating or hot water, rather than flagging an actual fault. D.007 Diagnostic This code indicates your boiler is simply reporting the current temperature setting for your hot water comfort mode, rather than showing a fault. D.008 Diagnostic Your boiler has lost the connection to its external heating controls, such as your thermostat or timer, preventing it from knowing when to turn on the heating. D.009 Diagnostic Your boiler is struggling to communicate correctly with its external controls, such as your room thermostat or smart controller. D.010 Diagnostic Your boiler is having trouble circulating water because the internal pump responsible for moving heat around your home has detected a wiring or electrical issue. D.011 Diagnostic Your boiler is having trouble communicating with the water pump that helps circulate heat around your home, which means it has stopped heating to prevent damage. D.012 Diagnostic Your boiler is struggling to pump hot water into your hot water cylinder, which means you may have no hot water available. D.013 Diagnostic Your boiler is struggling to push water around your radiators because it cannot detect that the internal water pump is working properly. D.014 Diagnostic Your boiler is struggling to communicate with the internal pump that moves hot water around your radiators and taps, causing it to stop operating correctly. D.015 Diagnostic Your boiler is struggling to confirm that the internal water pump is spinning at the correct speed to circulate heat through your radiators. D.016 Diagnostic Your boiler is currently operating normally and is confirming it has received a signal to turn on the heating. D.017 Diagnostic Your boiler's communication settings are currently mismatched or incorrectly configured, preventing it from talking to your heating controls properly. D.018 Diagnostic Your boiler is simply indicating that the internal water pump is currently running to move heat around your system. D.019 Diagnostic This code is simply an information display showing that your boiler's internal pump is currently set to run in a two-stage mode. D.020 Diagnostic Your boiler is currently monitoring or waiting for the hot water temperature to reach its target level, and this is typically a normal operating status rather than a breakdown. D.022 Diagnostic Your boiler is simply indicating that it has detected a request for hot water to be produced. D.023 Diagnostic Your boiler is currently just confirming that it is in heating mode and is waiting for the pump to reach the required speed before igniting. D.025 Diagnostic Your boiler is currently busy heating your hot water cylinder, which is a normal part of its routine operation. D.026 Diagnostic Your boiler has detected an issue with the internal electrical component that controls external accessories, such as an external pump or zone valve. D.027 Diagnostic Your boiler is struggling to communicate with an external add-on component, such as an external pump or a specialized heating zone controller. D.028 Diagnostic Your boiler is having trouble communicating with an add-on device, such as an external pump or a specialized heating zone control. D.033 Diagnostic Your boiler is struggling to detect or control the speed of the internal fan that pushes out waste gases. D.034 Diagnostic Your boiler is struggling to confirm that the internal fan, which clears exhaust gases safely, is spinning at the correct speed to operate. D.035 Diagnostic Your boiler is struggling to switch between heating your radiators and heating your hot water because an internal diverter valve is stuck or failing. D.036 Diagnostic Your boiler is struggling to detect or maintain the flow of hot water, which may cause your hot taps to run cold or the water temperature to fluctuate. D.039 Diagnostic Your boiler is receiving an unusual temperature reading from the solar thermal panel system connected to your hot water supply. D.040 Diagnostic Your boiler is simply reporting the current temperature of the water flowing through your system, which is a normal status update rather than a fault. D.041 Diagnostic Your boiler is struggling to accurately measure the temperature of the water returning to it from your radiators. D.044 Diagnostic Your boiler is struggling to detect the flame correctly, which prevents it from firing up reliably to heat your home. D.046 Diagnostic Your boiler is currently running a self-check on its internal water pump to ensure it is moving water around your heating system correctly. D.047 Diagnostic Your boiler is simply displaying the current temperature reading from an external weather sensor and is not indicating a fault. D.050 Diagnostic Your boiler is having trouble managing the speed of its internal fan, which is preventing it from running properly. D.051 Diagnostic Your boiler has detected an incorrect fan speed setting, which is preventing it from firing up correctly to provide heating or hot water. D.058 Diagnostic Your boiler is currently waiting for a signal from your solar hot water system to decide whether it needs to add extra heat to your water supply. D.060 Diagnostic Your boiler has detected that it has shut itself down due to overheating several times, suggesting an underlying issue with internal water circulation or heat dissipation. D.061 Diagnostic Your boiler has detected multiple failed attempts to light the burner and has temporarily stopped trying to prevent a potential gas buildup. D.064 Diagnostic Your boiler is struggling to ignite smoothly, which means it is taking longer than expected to establish a stable flame when it tries to start up. D.065 Diagnostic Your boiler has failed to light the flame within the allowed time frame, so it has safely shut itself down to prevent gas buildup. D.067 Diagnostic Your boiler is currently in a temporary rest period to prevent it from cycling on and off too frequently, and it will resume heating automatically shortly. D.068 Diagnostic Your boiler is struggling to ignite on the first try and is recording the number of times it has attempted to start up. D.069 Diagnostic Your boiler is struggling to ignite on the first try and is having to make a second attempt to get the flame going. D.070 Diagnostic Your boiler is struggling to switch between heating your radiators and heating your hot water because an internal diverter component is failing to move correctly. D.071 Diagnostic Your boiler has reached its maximum allowed heating temperature limit and is temporarily pausing to prevent overheating. D.072 Diagnostic Your boiler is briefly running its water pump to move excess heat away from the tank after it has finished heating your hot water, which is a normal part of the cooling process. D.073 Diagnostic Your boiler is currently recalibrating its internal temperature settings to ensure the water stays at the correct level of warmth, which is typically just a brief background process. D.075 Diagnostic Your boiler has taken too long to heat your hot water cylinder, causing it to pause the process to prevent the system from overheating. D.076 Diagnostic Your boiler has lost its unique digital identification code, meaning it no longer recognises its own configuration settings. D.077 Diagnostic Your boiler is currently running in a temporary mode that limits its power while heating your hot water, likely because it is adjusting to system demand. D.078 Diagnostic Your boiler is temporarily limiting the temperature of your hot water to protect itself from overheating while it performs an internal system check. D.080 Diagnostic This code is simply an information display showing the total number of hours your boiler has spent heating your radiators and is not a sign of a fault. D.081 Diagnostic This code is simply an information display showing the total number of hours your boiler has spent heating your domestic hot water, rather than indicating a fault. D.082 Diagnostic Your boiler is simply letting you know that it is currently in the process of starting up its burner to heat your home. D.083 Diagnostic Your boiler is simply performing a routine task to start heating up your hot water. D.084 Diagnostic Your boiler has reached its scheduled interval for a routine service check to ensure it remains efficient and safe. D.088 Diagnostic Your boiler is struggling to detect the flow of water needed to provide hot water to your taps, usually due to a blockage or a faulty sensor. D.090 Diagnostic Your boiler is having trouble communicating with the digital control panel or thermostat connected to it. D.091 Diagnostic Your boiler is struggling to pick up the radio signal that automatically sets its internal clock. D.093 Diagnostic Your boiler has lost its unique configuration settings, usually because the main control board has been replaced or reset and hasn't been programmed correctly for your specific model. D.094 Diagnostic Your boiler's memory of past errors has been successfully wiped and cleared. D.095 Diagnostic Your boiler is simply displaying a technical identification number for its internal software and is not actually experiencing a fault. D.096 Diagnostic Your boiler has reverted to its original factory settings, which means any personalised heating or hot water timings and temperatures you previously saved have been wiped and will need to be reconfigured. D.098 Diagnostic Your boiler has lost its unique electronic identity key, preventing it from knowing exactly which settings it should use to operate correctly. S.11 Status Your boiler is trying to heat your water, but the internal fan responsible for safety cannot get started. S.16 Status Your boiler's fan is still spinning after the hot water has been turned off, preventing the system from restarting safely. S.17 Status Your boiler is busy cooling itself down after providing hot water, but the water isn't moving through the system as quickly as it should.