Vaillant Boiler Fault Codes: Causes & Fixes
Vaillant boilers are popular for providing efficient heating and hot water in our homes. But if something goes wrong, the boiler displays an error code that helps you figure out what’s wrong.
Each error code means a different problem, such as a faulty sensor, low gas pressure, or something else.
Here is a complete list of all the Vaillant boiler error or fault codes, along with what they mean and how they might be fixed.
Vaillant Boiler Fault Codes and Their Solutions
F.49: eBus Fault (Voltage Too Low)
Causes: Your boiler’s communication bus (eBus) has low voltage, which is preventing proper communication between components.
Solutions: To resolve this issue, look for loose or disconnected eBus wiring. Check that no external equipment, such as thermostats, is interfering with communication. Restart the boiler and see whether the problem persists.
F.52 – Fault of Mass Flow Sensor Connection
Causes: The connection to the mass flow sensor of your boiler is faulty or disrupted.
Solutions: You need to check the sensor’s wiring and reconnect any loose cables. If the issue still remains, you should replace the sensor.
F.53 – Mass Flow Sensor Fault
Causes: A faulty mass flow sensor is affecting the boiler’s air/gas mixture regulation.
Solutions: First, you need to reset the boiler to see if the issue clears. However, if the fault still remains, replace the mass flow sensor.
F.54 – Fault of Gas Pressure
Causes: Low gas pressure, commonly associated with ignition failures (F.28, F.29).
Solutions: Check that the gas supply is turned on and that there are no blockages. If additional gas appliances are impacted, please contact your gas supplier. If just the boiler is impacted, contact a Gas Safe engineer.
F.56 – Mass Flow Sensor Regulation Fault
Causes: The F.56 error appears on your boiler when the mass flow sensor does not properly regulate airflow.
Solutions: First, clean the sensor and inspect for dirt or obstructions. If the sensor is malfunctioning, it should be replaced.
F.57 – Fault During Comfort Safety Mode
Causes: The Vaillant boiler problem code F57 often indicates a malfunction in the comfort safety mode, which is frequently associated with a heavily corroded ignition electrode.
Solutions: Reset the boiler. If the problem persists, you should call a Gas Safe Engineer.
F.76 – Overheating Protection Triggered
Causes: The primary heat exchanger has overheated, triggering the safety shutdown.
Solutions: Let the boiler cool down before restarting it. Check for clogged pipes or vents that are preventing water flow. If overheating persists, a professional check is required.
F.77 – Flue Non-Return Flap or Condensate Pump Fault
Causes: The boiler’s condensate pump or flue non-return flap is not working properly.
Solutions: Check the fuel for clogs and obstacles. Ensure that the condensate pipe is not frozen or obstructed.
F.78 – Interruption of DHW Outlet Sensor at External Controller
Causes: The Domestic Hot Water (DHW) outlet sensor does not communicate correctly with the external controller.
Solutions: Inspect the wire connections to the DHW sensor. If a sensor is defective, replace it.
F.83 – Flow and or Return Temperature Sensor Error
Causes: The flow and return temperature sensors do not detect temperature changes properly.
Solutions: To clear any temporary issues, reset your boiler. Inspect and replace defective sensors.
F.84 – Flow/Return Temperature Sensor Difference Error
Causes: The difference between the flow and return temperature sensors is wrong.
Solutions: You need to ensure that the sensors are appropriately fitted. If any of the sensors are malfunctioning, replace them.
F.85 – Flow and Return Temperature Sensors Incorrectly Fitted
Causes: The flow and return temperature sensors are put in the incorrect places.
Solutions: Swap the sensor placements to their proper places.
F.92 – Coding Resistor Fault
Causes: Your Vaillant boiler’s coding resistor is malfunctioning or missing.
Solutions: Check the resistor’s connection and replace it if needed.
F.93 – Gas Group Fault
Causes: The boiler is set up for the incorrect type of gas.
Solutions: Ensure that the gas type fits the boiler’s settings. To alter the settings, contact a Gas Safe engineer.
F.61 – Fault of Gas Valve Regulation
Causes: This error on your Vaillant Boiler occurs when the gas valve is not regulating gas flow correctly.
Solutions: First, you have to reset your boiler and see if the problem is fixed. If the problem remains, the gas valve may need replacement.
F.62 – Gas Valve Switch-Off Delay Error
Causes: The gas valve is taking too long to close, potentially resulting in leaks.
Solutions: Turn off both the boiler and the gas supply immediately. Call a Gas Safe engineer.
F.63: EEPROM Error
Causes: The boiler’s memory chip (EEPROM) has an issue.
Solutions: Restart your boiler. If the problem remains, the control board may require replacement.
F.64: Electronics/NTC Fault
Causes: An issue with your boiler’s electronics or the NTC temperature sensor can cause this error.
Solutions: Reset the boiler. Replace the NTC sensor as needed.
F.65: Electronic Temperature Fault
Causes: This error displays because of overheating or failure of an electrical circuit board.
Solutions: Ensure that the boiler is not overheating. If the problem continues, the circuit board may require replacement.
F.67: Electronics/Flame Fault
Causes: An issue with the flame detection system.
Solutions: Reset the boiler. If the problem persists, look for gas supply difficulties or ignition defects.
F.68: Unstable Flame Signal Error
Causes: The flame indication is inconsistent, maybe owing to gas or air supply difficulties.
Solutions: Ensure that the gas supply is steady. Inspect the burner for dirt or obstructions.
F.70: Invalid Device-Specific Number (DSN).
Causes: The boiler’s device number is wrong or unreadable.
Solutions: Reset the boiler. If the problem persists, the control board may require reprogramming.
F.71: Flow NTC Fault
Causes: The flow NTC sensor does not detect the proper temperature.
Solutions: Inspect and replace the sensor if required.
F.72: Flow/Return NTC Fault
Causes: A disparity between the flow and return NTC temperature measurements.
Solutions: Inspect and replace defective sensors.
F.73 and F.74: Water Pressure Sensor Faults
Causes: The water pressure sensor detects incorrect pressure.
Solutions: Check your boiler’s pressure gauge first. It should be set between 1.0 and 1.5 bar. If the pressure is low, repressurise the system. If the sensor doesn’t work properly, get it replaced by a Gas Safe engineer.
Still Need Help? Call a Gas Safe Engineer from PlusHeat
This is a detailed guide about Vaillant boiler error codes from our expert engineers, but if you think any boiler code might need immediate attention, then you can always contact us expert gas safe engineer, to fix your problem through our boiler service
Need help? Schedule an appointment today for your Vaillant boiler service!
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