Vokera A04 Fault

Vokera A04 Fault

The Vokèra A04 error code indicates an overheat fault within the boiler. This error occurs when the boiler’s water temperature exceeds the maximum safe limit. It’s a critical safety mechanism designed to prevent damage to the boiler and ensure safe operation. An overheat condition can be triggered by several issues within the heating system.

Causes of Vokèra A04 Error Code

  1. Blocked Heat Exchanger: Sludge or scale build-up in the heat exchanger can restrict water flow, leading to overheating as the heat cannot be dissipated effectively.
  2. Faulty Pump: A malfunctioning or seized pump can prevent proper circulation of water through the system, causing the water within the boiler to overheat.
  3. Restricted Water Flow: Closed valves or airlocks in the system can reduce water flow, contributing to overheating.
  4. Faulty Thermostat: A thermostat that fails to regulate the boiler’s temperature accurately can cause the system to overheat.

Troubleshooting and Resolving the Vokèra A04 Error Code

  1. Inspect the Heat Exchanger: Check for signs of sludge or scale. A professional system flush may be necessary to clear any blockages.
  2. Evaluate the Pump: Ensure the pump is operational. Listen for any unusual noises and feel for warmth, indicating it’s working. A non-operational or faulty pump will need professional attention.
  3. Check Water Flow: Verify that all valves in the system are fully open. Bleed radiators to remove any airlocks that could be impeding water circulation.
  4. Assess the Thermostat: Test the thermostat for proper operation. A faulty thermostat may need to be replaced by a qualified technician.
  5. Reset the Boiler: After addressing any issues, reset the boiler to clear the error code and reattempt operation. Consult the boiler manual for specific reset instructions.
  6. Seek Professional Help: If the A04 error persists or you’re unable to diagnose the issue, it’s advisable to contact a Gas Safe registered engineer. A professional can safely identify and repair the cause of the overheating.


The Vokèra A04 error code is an indication of an overheating issue that requires immediate attention to prevent potential damage to the boiler and ensure safe operation. While some preliminary checks can be performed by the homeowner, resolving the underlying cause of an overheat condition often necessitates professional intervention. Regular maintenance can help prevent such issues by ensuring that the heating system remains clean and all components are in good working order.