Vaillant Common Faults and Error Codes

Vaillant Common Faults and Error Codes

Vaillant boilers are known for their reliability and efficiency, but like any complex machinery, they can sometimes encounter issues that are indicated by specific fault or error codes. Understanding these codes can help diagnose problems early and, in some cases, allow homeowners to perform simple fixes. Here are some common Vaillant boiler fault or error codes and their meanings:

  1. F22: Low Water Pressure – This code appears when the water pressure in the system falls below the minimum required level, which can happen due to leaks or natural pressure loss over time.
  2. F28: Failure to Ignite – This error indicates that the boiler has failed to ignite, which could be due to issues with the gas supply, ignition electrodes, or a blocked flue.
  3. F29: Flame Goes Out – Similar to F28, this code signifies that the boiler’s flame has gone out after ignition, possibly due to gas supply issues or a fault with the flame detection system.
  4. F75: Pump/Water Pressure Sensor Fault – This code is shown when there’s a discrepancy between the water pressure sensor’s reading and the actual water pressure, often due to a problem with the pump or the sensor itself.
  5. F27: Flame Detection Fault When There Is No Flame – This indicates that the flame detection system is registering a flame when there shouldn’t be one, possibly due to a fault with the detection system.
  6. F32: Fan Speed Fault – This code appears when there’s an issue with the fan speed, either because the fan is not operating within the expected parameters or due to a fault in the fan’s operation.
  7. F62: Gas Valve Shut Off Delay – This error suggests that the gas valve is not closing at the expected time, potentially indicating a problem with the valve or the control board.
  8. F83: Flow and Return NTC Fault – This code indicates a discrepancy between the temperatures measured by the flow and return temperature sensors, possibly due to a fault with one of the sensors or issues with water circulation.

Troubleshooting and Resolution

  • F22 (Low Water Pressure): Check the pressure gauge and repressurize the system if necessary. Look for leaks in the system that might need fixing.
  • F28/F29 (Ignition Issues): Ensure there’s a gas supply to the boiler and check the flue for blockages. You may need a Gas Safe registered engineer to inspect the ignition system.
  • F75 (Pump/Water Pressure Sensor Fault): A professional may need to inspect the pump and water pressure sensor to determine if they need cleaning, repair, or replacement.
  • F27 (Faulty Flame Detection): This usually requires inspection by a professional to assess and repair or replace the flame detection system.
  • F32 (Fan Speed Fault): The fan will likely need to be inspected and possibly replaced by a Gas Safe registered engineer.
  • F62 (Gas Valve Shut Off Delay): A professional can test the gas valve and control board to identify and rectify the issue.
  • F83 (Flow and Return NTC Fault): Check for issues with water circulation and have a professional inspect or replace the temperature sensors as needed.


While some Vaillant boiler fault codes indicate problems that can be resolved with simple checks and adjustments, others require the expertise of a Gas Safe registered engineer. Regular maintenance and servicing can help prevent many common issues and ensure your boiler operates efficiently and safely.