Vokera A08 Fault

Vokera A08 Fault

The Vokèra A08 error code indicates a fault with the return thermistor. This sensor measures the temperature of the water returning to the boiler from the central heating system. A malfunction or discrepancy in the readings from this sensor can lead to issues with the boiler’s ability to regulate heating effectively, potentially causing the system to overheat or not heat adequately.

Causes of Vokèra A08 Error Code

  1. Faulty Return Thermistor: If the thermistor is malfunctioning or damaged, it may provide incorrect temperature readings to the boiler’s control unit.
  2. Wiring Issues: Problems with the wiring connections between the return thermistor and the boiler’s control board can disrupt the accurate transmission of temperature data.
  3. Sludge or Scale Build-up: Accumulation within the heating system, particularly around the thermistor, can affect its ability to accurately measure water temperature.
  4. Incorrect Installation or Placement: If the return thermistor is not correctly installed or has become dislodged, it may not accurately detect the return water temperature.

Troubleshooting and Resolving the Vokèra A08 Error Code

  1. Inspect the Return Thermistor: Check for any visible signs of damage to the return thermistor. It might need to be cleaned or replaced if it appears to be faulty.
  2. Check Wiring and Connections: Ensure that all connections between the return thermistor and the boiler’s control unit are secure and in good condition. Repair or replace any damaged wiring.
  3. Clear Sludge or Scale: If there’s sludge or scale build-up around the thermistor or within the system, consider having a professional flush the system to remove these obstructions.
  4. Verify Thermistor Placement: Make sure the return thermistor is correctly positioned as per the manufacturer’s guidelines. Adjustments or repositioning may require professional assistance.
  5. Reset the Boiler: After addressing any issues, try resetting the boiler to see if the error code clears and normal operation resumes.
  6. Seek Professional Assistance: If the A08 error persists or you’re unsure how to proceed, it’s advisable to contact a Gas Safe registered engineer. A professional can provide a more thorough diagnosis and, if necessary, replace the return thermistor.
  7. Regular Maintenance: To prevent future occurrences of the A08 error and other issues, ensure your heating system receives regular maintenance from a qualified technician. This can help identify and resolve potential problems early on.


The Vokèra A08 error code is an indication of a problem with the central heating return thermistor, necessitating prompt attention to maintain efficient and reliable boiler operation. While some preliminary checks and cleaning can be undertaken by homeowners, resolving issues related to the thermistor’s functionality or wiring typically necessitates professional intervention. Regular servicing can help maintain system performance and prevent similar faults.