Alpha E90 Fault

Alpha E90 Fault

The Alpha E90 error code indicates a pressure switch fault within the boiler. The pressure switch is a safety device that monitors the pressure within the boiler’s system to ensure it operates within safe limits. If the pressure switch detects an issue, such as too much or too little pressure, it can prevent the boiler from firing up to avoid damage or unsafe conditions.

Causes of Alpha E90 Error Code

  1. Faulty Pressure Switch: The switch itself may be malfunctioning, leading to incorrect readings or failure to operate as intended.
  2. Pressure Issues in the System: Abnormal pressure levels, either too high or too low, can trigger the pressure switch fault if the system is not operating within the designed pressure range.
  3. Blocked Vent or Flue: A blockage in the vent or flue can affect the pressure levels detected by the pressure switch.
  4. Wiring or Electrical Problems: Issues with the wiring or electrical connections to the pressure switch can result in malfunctioning or incorrect signals being sent to the boiler’s control unit.
  5. Air in the System: Air trapped in the heating system can also affect pressure levels and the operation of the pressure switch.

Troubleshooting and Resolving the Alpha E90 Error Code

  1. Inspect the Pressure Switch: Check the pressure switch for any visible signs of damage or malfunction. However, diagnosing a faulty pressure switch often requires professional tools and expertise.
  2. Check System Pressure: Ensure the boiler’s pressure is within the recommended range (usually between 1 and 1.5 bar). Adjust as necessary to maintain optimal pressure.
  3. Examine Vent and Flue: Look for any blockages or restrictions in the vent or flue that could affect the boiler’s pressure. Remove any obstructions found, if safe to do so.
  4. Check Wiring and Electrical Connections: Verify that all electrical connections to the pressure switch are secure and in good condition. Address any loose or damaged wiring.
  5. Bleed Radiators: Bleed any air from the radiators to eliminate airlocks in the system, which could influence pressure readings.
  6. Reset the Boiler: After addressing potential causes, attempt to reset the boiler to see if the error code clears and the boiler returns to normal operation.
  7. Professional Assistance: Due to the technical nature of diagnosing and fixing a pressure switch fault, it’s advisable to seek help from a Gas Safe registered engineer. A professional can accurately diagnose the issue and replace the pressure switch if necessary.


The Alpha E90 error code signifies a pressure switch fault, requiring careful attention to ensure the boiler operates safely and efficiently. While homeowners can perform basic checks and adjustments, resolving the underlying cause of a pressure switch fault typically necessitates professional intervention. Regular boiler maintenance can help prevent such issues by ensuring the system operates within the correct pressure range and all components are in good working order.