Vaillant ecoTEC pro Boilers
45 fault codes documented
F.00 — Flow temperature sensor interruption
The boiler has detected an interruption in the flow temperature sensor circuit. This means the boiler cannot accurately measure the temperature of the water leaving it.
F.01 — Return temperature sensor interruption
The boiler has detected an interruption in the return temperature sensor circuit. This prevents the boiler from accurately measuring the temperature of the water returning to it.
F.10 — Flow NTC short circuit
The flow temperature sensor circuit has a short circuit. This prevents the boiler from accurately reading the flow temperature, which can lead to incorrect operation.
F.11 — Return NTC short circuit
The return temperature sensor circuit has a short circuit. This prevents the boiler from accurately reading the return temperature, which can lead to incorrect operation.
F.20 — Safety switch-off: Temperature limiter triggered
The safety temperature limiter has activated, causing the boiler to switch off. This typically happens if the boiler detects an unsafe overheating condition.
F.22 / Flashing pressure value - Heating system water pressure too low
The boiler display shows the fault message F.22, or the current pressure value flashes. This indicates that the water pressure in the heating system has fallen too low. If the pressure drops below 0.5 bar, the boiler will switch off.
F.23 — Safety switch-off: Temperature difference too great
The boiler has detected an excessively large temperature difference between the flow and return pipes, indicating a circulation problem. This triggers a safety shutdown.
F.24 — Safety switch-off: Temperature rise too fast
The boiler has shut down because the temperature of the water is rising too rapidly. This indicates a problem with water circulation or flow within the system.
F.25 — Safety switch-off: Flue gas temperature too high
The boiler has shut down because the flue gas temperature has exceeded safe limits. This is a safety measure to prevent overheating of the flue system.
F.26 — Fault: Gas valve without function
The boiler has detected that the gas valve is not functioning correctly, which prevents it from regulating the gas supply to the burner.
F.27 — Safety switch-off: Flame simulation
The boiler has detected a 'flame simulation', meaning it registers a flame even when the burner is not supposed to be active. This is a safety shutdown.
F.28 — Failure during start-up: Ignition unsuccessful
The boiler failed to ignite successfully during its start-up sequence. This means it couldn't establish a flame to begin heating.
F.29 — Failure during operation: Re-ignition unsuccessful
The boiler's flame extinguished during operation, and it failed to re-ignite. This results in the boiler shutting down for safety.
F.32 — Fan fault
The boiler has detected a fault with its internal fan. The fan is crucial for safely expelling combustion gases and drawing in fresh air.
F.49 — eBUS fault
A fault has occurred in the eBUS communication system, which connects the boiler to external controls and accessories. This can prevent proper communication.
F.61 — Fault: Gas valve regulation
The boiler's gas valve regulation system is faulty. This means the boiler cannot correctly control the flow of gas, which is essential for safe operation.
F.62 — Fault: Gas valve switch-off delay
The boiler has detected a delayed shutdown of the gas valve or a delayed extinguishing of the flame signal. This is a safety concern as gas flow should stop immediately when required.
F.63 — EEPROM error
An error has occurred with the EEPROM (Electrically Erasable Programmable Read-Only Memory), which stores critical configuration data for the boiler's electronics.
F.64 — Electronics/NTC fault
The boiler's electronics or an NTC (Negative Temperature Coefficient) sensor has developed a fault. This could affect temperature readings or overall boiler control.
F.65 — Electronic temperature fault
The boiler's electronic components have detected an abnormal temperature, possibly due to overheating from external factors or an internal component failure.
F.67 — Electronics/flame fault
The boiler's electronics have detected an implausible flame signal, meaning the flame sensing is incorrect or inconsistent. This is a safety measure to prevent unsafe operation.
F.68 — Unstable flame signal fault
The boiler has detected an unstable flame signal, indicating that the flame is not burning consistently or reliably. This can lead to inefficient operation or safety shutdowns.
F.70 — Invalid device specific number (DSN)
This fault typically occurs after replacement of both the display and the main PCB, where the appliance code (DSN) was not correctly reset by the installer.
F.71 — Flow NTC fault
The flow temperature sensor is signaling a constant or unchanging value, indicating it is either faulty or incorrectly positioned and unable to detect temperature changes.
F.72 — Flow/return NTC fault
The boiler has detected an implausibly large temperature difference between the flow and return NTC sensors, suggesting one or both sensors are faulty.
F.73 — Water pressure sensor signal too low
The water pressure sensor is sending a signal that is too low, indicating a problem with the sensor itself or its wiring.
F.74 — Water pressure sensor signal too high
The water pressure sensor is sending a signal that is outside the correct range and too high. This can be due to wiring issues or a faulty sensor.
F.75 — Fault: No pressure change detection when starting pump
The boiler has failed to detect a change in water pressure when the pump starts, indicating a circulation problem or a faulty sensor/pump. The boiler may be unable to circulate water effectively.
F.76 — Overheating protection on primary heat exchanger responded
The overheating protection device on the primary heat exchanger has been activated, indicating an extreme overheating event. This is a critical safety shutdown.
F.77 — Flue non-return flap/condensate pump fault
The boiler has detected a fault with either the flue non-return flap or the condensate pump. Both are vital for safe and efficient operation of the flue system.
F.78 — Interruption to DHW outlet sensor at external controller
This fault indicates an interruption with the Domestic Hot Water (DHW) outlet sensor, particularly when an external controller is connected using a UK link box, and the hot water NTC is not correctly bridged.
F.83 — Flow and/or return temperature sensor temperature change fault
When the burner starts, the boiler fails to register a sufficient temperature change at either the flow or return temperature sensors. This indicates a problem with water circulation or sensor positioning.
F.84 — Fault: Flow/return temperature sensor temperature difference implausible
The boiler's flow and return temperature sensors are reporting implausible or inconsistent temperature differences. This could be due to incorrect installation or faulty sensors.
F.85 — Fault: Flow and return temperature sensors incorrectly fitted
The boiler has detected that the flow and return temperature sensors are incorrectly fitted, possibly to the same pipe or the wrong pipes. This prevents accurate temperature measurement.
Fault symbol on display - Boiler is in an error condition
A specific fault symbol appears in the bottom left corner of the boiler's display. This indicates that the boiler is in a general error condition and cannot start any test programs.
Ignition problems — Boiler fails to ignite due to unpurged gas tank
The boiler may experience ignition problems if the liquid gas tank was not properly purged during the system installation. This prevents the boiler from starting correctly.
No communication with PCB — Communication fault between display and PCB
The display is unable to communicate with the main Printed Circuit Board (PCB) in the electronics box. This means the boiler cannot receive or send control signals or display information correctly.
Open-end spanner symbol — Service message present
The open-end spanner maintenance symbol on the display indicates that a service interval has elapsed. The boiler is not in fault mode and will continue to operate, but it is recommended to check for more information.
S.30 — Room thermostat blocking heating mode
The room thermostat is preventing the boiler from entering heating mode. This could be due to the thermostat being set too low or scheduled off.
S.31 — Summer mode active or no heat requirement
The boiler is either in summer mode, which typically disables heating, or there is no active demand for heat from your eBUS controller.
S.41 — Water pressure too high (> 2.8 bar)
The boiler's internal water pressure has exceeded the safe limit of 2.8 bar. High pressure can indicate an issue within the heating system.
S.76 — System pressure too low, top up water
The display shows that the system pressure is too low, indicating that water needs to be added to the boiler. The boiler may not operate until the pressure is corrected.
Smell of exhaust fumes — Potential flue gas leak and poisoning risk
Detecting a smell of exhaust fumes indicates a potential flue gas leak, which carries a risk of poisoning. This can be caused by installation errors, damage, or unauthorized installation sites.
Smell of gas — Potential gas leak and explosion risk
If you detect a smell of gas in the building, this indicates a potential gas leak, carrying a risk of poisoning and explosion. This can be caused by installation errors, damage, or tampering.
Fault shutdown or unusual noise — Using incorrect gas type
The boiler may shut down or operate with unusual ignition and combustion noise if the incorrect type of gas is being used. This can prevent proper and safe operation of the appliance.