Vaillant Boiler Fault Codes Explained with Resolutions
Understanding Vaillant Boiler Fault Codes
When it comes to heating systems, Vaillant boilers have established themselves as one of the most reliable and efficient systems around. However, like any complex machinery, these boilers occasionally encounter technical hiccups that can disrupt their smooth operation. Fortunately, Vaillant has a sophisticated error code system, designed to help homeowners diagnose and troubleshoot common issues.
In this blog, we aim to demystify the world of Vaillant boiler codes, providing you with a comprehensive understanding of the technical error and fault messages that may appear. But fear not, we won't be drowning you in technical jargon. Our goal is to simplify these codes, explaining them in plain and accessible language, ensuring that you can comprehend and rectify the issues with confidence.
Remember, diagnosing and fixing technical issues with your Vaillant boiler doesn't have to be a daunting task. With a bit of knowledge and the right approach, you can address these challenges and restore your heating system's optimal performance. So, let's dive into the world of Vaillant boiler codes, decode their meanings.
Vaillant Boiler Fault Code F.00: Flow sensor interruption
What does Vaillant Boiler fault code F.01 mean?
Fault code F.00 indicates an interruption in the flow sensor. This could be due to the NTC plug not being plugged in or coming loose, incorrect connection of multiple plugs on the PCB, interruption in the cable harness, or a defective NTC sensor.
How to fix Vaillant Boiler fault code F.00
To fix this issue, ensure that the NTC plug is securely connected, check the PCB for any loose plugs, inspect the cable harness for any interruptions, and if needed, replace the NTC sensor.
Vaillant Boiler Fault Code F.01: Return sensor interruption
What does Vaillant Boiler fault code F.01 mean?
Fault code F.01 indicates an interruption in the return sensor. This could be caused by the NTC plug not being plugged in or coming loose, incorrect connection of multiple plugs on the PCB, interruption in the cable harness, or a defective NTC sensor.
How to fix Vaillant Boiler fault code F.01
To resolve this issue, ensure that the NTC plug is properly connected, check the PCB for any loose plugs, inspect the cable harness for interruptions, and if necessary, replace the NTC sensor.
Vaillant Boiler Fault Code F.02: DHW outlet sensor interruption
What does Vaillant Boiler fault code F.02 mean?
Fault code F.02 indicates an interruption in the DHW (Domestic Hot Water) outlet sensor. This can be caused by a defective NTC, defective NTC cable, faulty plug connection on the NTC, or a defective plug connection on the actoSTOR electronics. This fault code is applicable only when it occurs in conjunction with fault code F.91.
How to fix Vaillant Boiler fault code F.02
To fix this issue, check and replace the faulty NTC or NTC cable, ensure proper plug connections, and if needed, repair or replace the actoSTOR electronics.
Vaillant Boiler Fault Code F.03: Cylinder sensor interruption
What does Vaillant Boiler fault code F.03 mean?
Fault code F.03 indicates an interruption in the cylinder sensor. This can occur due to a defective NTC, defective NTC cable, faulty plug connection on the NTC, or a defective plug connection on the actoSTOR electronics. This fault code is relevant only when it occurs alongside fault code F.91.
How to fix Vaillant Boiler fault code F.03
To resolve this issue, check and replace any faulty NTC or NTC cables, ensure proper plug connections, and if necessary, repair or replace the actoSTOR electronics.
Vaillant Boiler Fault Code F.10: Flow sensor short circuit
What does Vaillant Boiler fault code F.10 mean?
Fault code F.10 indicates a short circuit in the flow sensor. This can be caused by a defective NTC, a short circuit in the cable harness, or damage to the cable or casing.
How to fix Vaillant Boiler fault code F.10
To fix this issue, check and replace the faulty NTC, inspect the cable harness for any short circuits, and repair or replace any damaged cables or casings.
Vaillant Boiler Fault Code F.11: Return sensor short circuit
What does Vaillant Boiler fault code F.11 mean?
Fault code F.11 indicates a short circuit in the return sensor. This can occur due to a defective NTC, a short circuit in the cable harness, or damage to the cable or casing.
How to fix Vaillant Boiler fault code F.11
To resolve this issue, check and replace the faulty NTC, inspect the cable harness for any short circuits, and repair or replace any damaged cables or casings.
Vaillant Boiler Fault Code F.12: DHW outlet sensor short circuit
What does Vaillant Boiler fault code F.12 mean?
Fault code F.12 indicates a short circuit in the DHW outlet sensor. This can be caused by a defective NTC, a short circuit in the cable harness, or damage to the cable or casing. This fault code is relevant only when it occurs in conjunction with fault code F.91.
How to fix Vaillant Boiler fault code F.12
To fix this issue, check and replace the faulty NTC, inspect the cable harness for any short circuits, and repair or replace any damaged cables or casings.
Vaillant Boiler Fault Code F.13: Cylinder sensor short circuit
What does Vaillant Boiler fault code F.13 mean?
Fault code F.13 indicates a short circuit in the cylinder sensor. In a combination product with a warm start sensor or actoSTOR, it can be caused by a short circuit between the warm start sensor and the cylinder sensor. This fault code is relevant only when it occurs in combination with fault code F.91. The issue can also be due to a defective NTC, a short circuit in the cable harness, or damage to the cable or casing.
How to fix Vaillant Boiler fault code F.13
To resolve this issue, check and replace the faulty NTC, inspect the cable harness for any short circuits, repair or replace any damaged cables or casings, and if applicable, ensure there is no short circuit between the warm start sensor and cylinder sensor.
Vaillant Boiler Fault Code F.20 - Temperature limiter
What does Vaillant Boiler fault code F.20mean?
Fault code F.20 indicates a safety switch-off due to an incorrect earth connection between the cable harness and the product, a defective flow or return NTC (temperature sensor) with a loose connection, or black discharge via the ignition cable, ignition plug, or ignition electrode.
How to fix Vaillant Boiler fault code F.20
To fix this issue, check and ensure a proper earth connection, tighten any loose connections, and inspect the ignition components for any black discharge or damage. Replace any faulty components as necessary.
Vaillant Boiler Fault Code F.22 - Low water pressure
What does Vaillant Boiler fault code F.22 mean?
Fault code F.22 indicates a safety switch-off due to low water pressure, which can be caused by no or insufficient water in the product or a defective water pressure sensor.
How to fix Vaillant Boiler fault code F.22
To resolve this issue, check the water supply to the product and ensure it is sufficient. If the water pressure is low or there is no water in the product, refill or restore it to the proper level. Additionally, inspect and replace the water pressure sensor if necessary.
Vaillant Boiler Fault Code F.23 - Temp.spread too large
What does Vaillant Boiler fault code F.23 mean?
Fault code F.23 indicates a safety switch-off due to the temperature spread being too large. This can be caused by a blocked pump, insufficient pump output, air in the product, or incorrect connection of the flow and return NTC (temperature sensors).
How to fix Vaillant Boiler fault code F.23
To fix this issue, check and clear any blockages in the pump, ensure proper pump output, bleed out any air from the product, and verify correct connection of the flow and return NTC.
Vaillant Boiler Fault Code F.24 - Temp. incr. too fast
What does Vaillant Boiler fault code F.24 mean?
Fault code F.24 indicates a safety switch-off due to the temperature increasing too rapidly. This can be caused by a blocked pump, insufficient pump output, air in the product, low system pressure, or a blocked or incorrectly installed non-return valve.
How to fix Vaillant Boiler fault code F.24
To resolve this issue, check and clear any pump blockages, ensure sufficient pump output, bleed out any air from the product, increase the system pressure if it's low, and inspect or replace the non-return valve if necessary.
Vaillant Boiler Fault Code F.25 - Flue temp. too high
What does Vaillant Boiler fault code F.25 mean?
Fault code F.25 indicates a safety switch-off due to the flue gas temperature being too high. This can be caused by a break in the plug connection for the optional flue gas safety temperature limiter (STB) or a break in the cable harness
How to fix Vaillant Boiler fault code F.25
To fix this issue, check the plug connection for any breaks or loose connections, and inspect the cable harness for any damage. Repair or replace any faulty components as needed.
Vaillant Boiler Fault Code F.26 - Fuel valve not working
What does Vaillant Boiler fault code F.26 mean?
Fault code F.26 indicates a fault with the fuel valve, specifically the gas valve stepper motor. This can be caused by the stepper motor not being connected properly, a loose multiple plug on the PCB (printed circuit board), an interruption in the cable harness, or a defective gas valve stepper motor or electronics.
How to fix Vaillant Boiler fault code F.26
To resolve this issue, check and ensure the gas valve stepper motor is connected correctly, secure the multiple plug on the PCB, inspect the cable harness for any interruptions, and if necessary, replace the gas valve stepper motor or faulty electronics.
Vaillant Boiler Fault Code F.27 - Flame simulation
What does Vaillant Boiler fault code F.27 mean?
Fault code F.27 indicates a safety switch-off due to flame simulation. This can be caused by moisture on the electronics, defective electronics (specifically the flame monitor), or a gas solenoid valve leakage.
How to fix Vaillant Boiler fault code F.27
To resolve this issue, remove any moisture from the electronics, replace the defective electronics or flame monitor, and repair or replace the gas solenoid valve if it is leaking.
Vaillant Boiler Fault Code F.28 - Start-up failure
What does Vaillant Boiler fault code F.28 mean?
Fault code F.28 indicates a start-up failure with unsuccessful ignition. This can be caused by various factors such as a defective gas meter or pressure monitor, air in the gas supply, low gas flow pressure, triggered thermal isolator device, blocked condensate duct, incorrect gas restrictor or spare part gas valve, faulty gas valve or ignition system components, incorrect earthing, or defective electronics.
How to fix Vaillant Boiler fault code F.28
To fix this issue, check and replace any faulty components mentioned above, clear any blockages, ensure proper gas flow and pressure, and verify correct earthing connections.
Vaillant Boiler Fault Code F.29 - Start-up failure
What does Vaillant Boiler fault code F.29 mean?
Fault code F.29 indicates a start-up failure with unsuccessful ignition. This can be caused by a temporary stoppage in the gas supply, flue gas recirculation, blocked condensate duct, defective earthing, or spark failure in the ignition transformer.
How to fix Vaillant Boiler fault code F.29
To resolve this issue, ensure the gas supply is not interrupted, check for any obstructions in the flue gas recirculation or condensate duct, verify proper earthing, and if necessary, replace the faulty ignition transformer.
Vaillant Boiler Fault Code F.32 - Fan fault
What does Vaillant Boiler fault code F.32 mean?
Fault code F.32 indicates a fan fault. This can be caused by the fan plug not being correctly plugged in, the multiple plug on the PCB not being correctly plugged in, a break in the cable harness, a blocked fan, or a defective Hall sensor or electronics.
How to fix Vaillant Boiler fault code F.32
To fix this issue, ensure the fan plug and multiple plug on the PCB are correctly connected, inspect the cable harness for any breaks, clear any obstructions in the fan, and if necessary, replace the faulty Hall sensor or electronics.
Vaillant Boiler Fault Code F.49 - eBUS fault
What does Vaillant Boiler fault code F.49 mean?
Fault code F.49 indicates an eBUS fault. This can be caused by a short circuit on the eBUS, eBUS overload, or two power supplies with different polarities connected to the eBUS.
How to fix Vaillant Boiler fault code F.49
To resolve this issue, check for any short circuits or overload conditions on the eBUS, and ensure that only one power supply with the correct polarity is connected to the eBUS.
Vaillant Boiler Fault Code F.52 - Mass flow sensor/Venturi contact fault
What does Vaillant Boiler fault code F.52 mean?
Fault code F.52 indicates a contact fault with the mass flow sensor/Venturi. This can be caused by an electrical connection issue, incorrect plug insertion, defective plug or slot, or a defective mass flow sensor/Venturi.
How to fix Vaillant Boiler fault code F.52
To fix this issue, ensure that the electrical plug is connected properly, check for any defects in the plug or slot, and if necessary, replace the faulty mass flow sensor/Venturi.
Vaillant Boiler Fault Code F.53 - Combustion regulation fault
What does Vaillant Boiler fault code F.53 mean?
Fault code F.53 indicates a combustion regulation fault. This can be caused by a fault detected in the combustion regulation system, low gas flow pressure, incorrect coding resistance (e.g., using liquid gas resistance with natural gas), or faulty gas valve or mass flow sensor/Venturi.
How to fix Vaillant Boiler fault code F.53
To resolve this issue, check and address any faults in the combustion regulation system, ensure proper gas flow pressure, use the correct coding resistance, and if necessary, replace the faulty gas valve or mass flow sensor/Venturi.
Vaillant Boiler Fault Code F.54 - Gas supply fault
What does Vaillant Boiler fault code F.54 mean?
Fault code F.54 indicates a gas supply fault, typically in combination with fault codes F.28 or F.29. This fault suggests there is insufficient gas supply to operate the unit, which can be due to a closed gas isolator cock, low gas flow pressure, or a faulty gas valve.
How to fix Vaillant Boiler fault code F.54
To fix this issue, ensure the gas isolator cock is open, verify sufficient gas flow pressure, and if necessary, replace the faulty gas valve.
Vaillant Boiler Fault Code F.56 - Safety switch-off
What does Vaillant Boiler fault code F.56 mean?
Fault code F.56 indicates a safety switch-off due to the carbon monoxide (CO) limit being exceeded. This typically occurs when a component in the combustion regulation system is defective.
How to fix Vaillant Boiler fault code F.56
To address this issue, check for any contact faults at the gas valve (such as incorrect or faulty plug connection) and ensure they are securely connected. If the fault persists after troubleshooting, the gas valve may be defective and require replacement.
Vaillant Boiler Fault Code F.57 - Measuring program
What does Vaillant Boiler fault code F.57 mean?
Fault code F.57 indicates a fault in the measuring program, where the active comfort protection mode has detected a regulation fault. This can be caused by a highly corroded ignition electrode.
How to fix Vaillant Boiler fault code F.57
To resolve this issue, inspect and clean the ignition electrode. If the corrosion is severe or cleaning doesn't fix the problem, it may be necessary to replace the ignition electrode.
Vaillant Boiler Fault Code F.61 - Fuel valve actuation
What does Vaillant Boiler fault code F.61 mean?
Fault code F.61 indicates a fault in the fuel valve actuation. This can be caused by a defective cable harness supply line to the gas valve (such as a short circuit or short to earth), a faulty gas valve, or a defective PCB (printed circuit board).
How to fix Vaillant Boiler fault code F.61
To address this issue, check the cable harness for any wiring issues, replace the gas valve if necessary, and if the problem persists, consider replacing the PCB.
Vaillant Boiler Fault Code F.62 - Fuel valve switch-off delay
What does Vaillant Boiler fault code F.62 mean?
Fault code F.62 indicates a delayed shutdown of the gas valve has been detected. This can be indicated by the secondary light (ignition and monitoring electrode) showing a delayed extinguishing of the flame signal. Possible causes include a defective gas valve or a faulty PCB.
How to fix Vaillant Boiler fault code F.62
To resolve this issue, inspect and replace the gas valve if necessary, and if the problem persists, consider replacing the PCB.
Vaillant Boiler Fault Code F.63 - EEPROM
What does Vaillant Boiler fault code F.63 mean?
Fault code F.63 indicates a fault in the EEPROM (Electrically Erasable Programmable Read-Only Memory) of the electronics. This generally points to defective electronics.
How to fix Vaillant Boiler fault code F.63
To resolve this issue, the electronics unit will likely need to be replaced.
Vaillant Boiler Fault Code F.64 - Electronics/sensor
What does Vaillant Boiler fault code F.64 mean?
Fault code F.64 indicates a fault related to the flow or return NTC (Negative Temperature Coefficient) sensor being short-circuited, or defective electronics. To fix this issue, check the wiring and connections of the NTC sensor, and if necessary, replace the sensor.
How to fix Vaillant Boiler fault code F.64
If the fault persists, the electronics unit may be defective and require replacement.
Vaillant Boiler Fault Code F.65 - Electronics temperature
What does Vaillant Boiler fault code F.65 mean?
Fault code F.65 indicates that the electronics are overheating due to external influences. This can be caused by factors such as poor ventilation or high ambient temperatures. Check the surroundings of the unit to ensure proper ventilation and cooling.
How to fix Vaillant Boiler fault code F.65
If the issue persists, the electronics unit may be defective and require replacement.
Vaillant Boiler Fault Code F.67 - Electronics/flame
What does Vaillant Boiler fault code F.67 mean?
Fault code F.67 indicates an implausible flame signal detected by the electronics. This can be caused by defective electronics.
How to fix Vaillant Boiler fault code F.67
To resolve this issue, the electronics unit will likely need to be replaced.
Vaillant Boiler Fault Code F.68 - Flame signal unstable
What does Vaillant Boiler fault code F.68 mean?
Fault code F.68 indicates an unstable flame signal. Possible causes include air in the gas supply, low gas flow pressure, incorrect air-fuel ratio, blocked condensate duct, interruption in ionization flow (e.g., cable or electrode issue), flue gas recirculation, or a blocked condensate duct.
How to fix Vaillant Boiler fault code F.68
Check the gas supply, ensure proper gas flow pressure, inspect the condensate duct, and address any issues with the ionization flow.
Vaillant Boiler Fault Code F.70 - Invalid Device Specific Number
What does Vaillant Boiler fault code F.70 mean?
Fault code F.70 indicates an invalid Device Specific Number (DSN). This can occur when a display and PCB (printed circuit board) are replaced at the same time without resetting the DSN, or when there is incorrect or missing output range coding resistance.
How to fix Vaillant Boiler fault code F.70
To resolve this issue, ensure the DSN is correctly set and verify the proper coding resistance for the output range.
Vaillant Boiler Fault Code F.71 - Flow sensor
What does Vaillant Boiler fault code F.71 mean?
Fault code F.71 indicates a constant value signaling from the flow temperature sensor. This can be caused by the flow temperature sensor being incorrectly positioned at the supply pipe or a defective flow temperature sensor. Check the position of the flow temperature sensor and ensure it is properly placed.
How to fix Vaillant Boiler fault code F.71
If the fault persists, consider replacing the flow temperature sensor.
Vaillant Boiler Fault Code F.72 - Flow/return sensor
What does Vaillant Boiler fault code F.72 mean?
Fault code F.72 indicates a temperature difference that is too great between the flow and return sensors. This can be an indication of a defective flow or return temperature sensor.
How to fix Vaillant Boiler fault code F.72
To fix this issue, check the sensors and replace any that are found to be defective.
Vaillant Boiler Fault Code F.73 - Water press. sensor
What does Vaillant Boiler fault code F.73 mean?
Fault code F.73 indicates an interruption or short circuit of the water pressure sensor, or an interruption or short circuit to the ground in the supply line to the water pressure sensor. It can also indicate a defective water pressure sensor.
How to fix Vaillant Boiler fault code F.73
Inspect the wiring and connections to the water pressure sensor, ensuring they are intact. If any faults are found, address them accordingly. If necessary, replace the water pressure sensor.
Vaillant Boiler Fault Code F.74 - Water pressure sensor
What does Vaillant Boiler fault code F.74 mean?
Fault code F.74 indicates a short circuit between the line to the water pressure sensor and 5 V/24 V, or an internal fault in the water pressure sensor. Check the wiring of the water pressure sensor to ensure there are no short circuits.
How to fix Vaillant Boiler fault code F.74
If the fault persists, the water pressure sensor may be defective and require replacement.
Vaillant Boiler Fault Code F.75 - Pump/water shortage
What does Vaillant Boiler fault code F.75 mean?
Fault code F.75 indicates a pump or water shortage issue. This can be caused by a defective water pressure sensor, air in the heating installation, or insufficient water in the system.
How to fix Vaillant Boiler fault code F.75
To fix this issue, check the water pressure sensor and pump for any defects. Additionally, ensure there is no air trapped in the heating system and that there is enough water in the system. If needed, connect an external expansion vessel to the return line.
Vaillant Boiler Fault Code F.77 - Flue non-ret. valve/condens. pump
What does Vaillant Boiler fault code F.77 mean?
Fault code F.77 indicates a lack of response from the flue non-return flap or a defective condensate pump
How to fix Vaillant Boiler fault code F.77
To resolve this issue, check the operation of the flue non-return flap and replace it if necessary. Additionally, inspect the condensate pump for any defects and replace it if needed.
Vaillant Boiler Fault Code F.78 - Interrupt.: DHW outlet sensor on ext. contr
What does Vaillant Boiler fault code F.78 mean?
Fault code F.78 indicates an interruption in the DHW (Domestic Hot Water) outlet sensor on the external control unit. This can occur when the UK link box is connected, but the hot water NTC (Negative Temperature Coefficient) is not bridged.
How to fix Vaillant Boiler fault code F.78
Check the connection and ensure the hot water NTC is properly bridged to resolve this issue.
Vaillant Boiler Fault Code F.80 - actoSTOR inlet sensor
What does Vaillant Boiler fault code F.80 mean?
Fault code F.80 indicates a fault in the actoSTOR inlet sensor. This can be caused by a defective NTC (Negative Temperature Coefficient) sensor, defective NTC cable, faulty plug connection on the NTC or actoSTOR electronics, or a short circuit between the sensor plug and the casing.
How to fix Vaillant Boiler fault code F.80
Check the NTC and cables for any defects, ensure proper plug connections, and address any short circuits. If necessary, replace the faulty components.
Vaillant Boiler Fault Code F.81 - Cylinder charging pump
What does Vaillant Boiler fault code F.81 mean?
Fault code F.81 indicates a fault in the cylinder charging pump. This occurs when the cylinder is not fully charged within the specified time.
How to fix Vaillant Boiler fault code F.81
To resolve this issue, check the cylinder charging sensor and cylinder sensor for any defects. Additionally, inspect the cable harness for the pump and ensure proper functioning of the impeller sensor and limiter. Check for any blockages in the secondary heat exchanger and consider replacing the diverter valve or faulty pump if necessary.
Vaillant Boiler Fault Code F.83 - NTC temp. gradient
What does Vaillant Boiler fault code F.83 mean?
Fault code F.83 indicates a lack of or insufficient temperature change detected by the flow and/or return temperature sensors when the burner starts. This can be caused by insufficient water in the system or incorrect positioning of the flow or return temperature sensor.
How to fix Vaillant Boiler fault code F.83
Ensure there is enough water in the system and check the proper placement of the temperature sensors.
Vaillant Boiler Fault Code F.84 - NTC temp. diff. Implausible
What does Vaillant Boiler fault code F.84 mean?
Fault code F.84 indicates implausible values detected by the flow and return temperature sensors. This can occur when the sensors have been inverted or incorrectly installed.
How to fix Vaillant Boiler fault code F.84
This can occur when the sensors have been inverted or incorrectly installed. Check the placement of the flow and return temperature sensors and ensure they are installed correctly.
Vaillant Boiler Fault Code F.85 - NTCs fitted incorrectly
What does Vaillant Boiler fault code F.85 mean?
Fault code F.85 indicates that the flow and/or return temperature sensors have been installed on the same pipe or an incorrect pipe.
How to fix Vaillant Boiler fault code F.85
To fix this issue, reposition the temperature sensors so that they are installed correctly, each on their respective pipes.
Vaillant Boiler Fault Code F.90 - Communication
What does Vaillant Boiler fault code F.90 mean?
Fault code F.90 indicates a communication issue. Check the cable harness from the product to the actoSTOR module (PEBus) for any faults or loose connections.
How to fix Vaillant Boiler fault code F.90
If the product is not intended to be used with an actoSTOR module, set the parameter D.092 to 0.
Vaillant Boiler Fault Code F.91 - Sensor/actuator fault on actoSTOR module
What does Vaillant Boiler fault code F.91 mean?
Fault code F.91 indicates a sensor or actuator fault on the actoSTOR module.
How to fix Vaillant Boiler fault code F.91
This requires further investigation and troubleshooting by a qualified technician. Contact a professional service to diagnose and repair the actoSTOR module.
Vaillant Boiler Fault Code F.92 - Coding resistance fault
What does Vaillant Boiler fault code F.92 mean?
Fault code F.92 indicates a coding resistance fault. This occurs when the coding resistance on the PCB does not match the entered gas group.
How to fix Vaillant Boiler fault code F.92
Check the resistance, repeat the gas family check, and enter the correct gas group to resolve this issue.
Vaillant Boiler Fault Code F.93 - Poor combustion quality
What does Vaillant Boiler fault code F.93 mean?
Fault code F.93 indicates that the combustion regulation system has detected poor combustion quality. Possible causes include an incorrect gas restrictor installed for the gas family or issues with recirculation or the mass flow sensor/venturi.
How to fix Vaillant Boiler fault code F.93
Ensure the correct gas restrictor is installed, avoid wetting the sensor or using lubricants on the venturi's O-ring, and address any recirculation issues. If necessary, replace the mass flow sensor or venturi.
