worcester greenstar diverter valve problems

Worcester Greenstar boilers are known for their efficiency and reliability. However, like any complex machinery, they can experience specific issues, particularly with the diverter valve. This article explores the common problems associated with the diverter valve in Worcester Greenstar boilers, particularly the 20/25 oil-fired storage combi boiler, and offers practical solutions.

Understanding Diverter Valve Malfunction in Worcester Greenstar Boilers

  1. Symptoms of a Faulty Diverter Valve: A common issue with Worcester Greenstar boilers is the central heating system working fine but the domestic hot water running cold. The boiler starts up, with the pump and burner fan activating, but the hot water tap only runs warm for a second before turning cold.
  2. Potential Causes of the Issue: This problem is often linked to the diverter valve, especially when the valve lever feels loose and doesn’t spring to one side, indicating a possible spring failure or a malfunction in the valve mechanism.

Diagnosing and Addressing the Problem

  1. Checking the Diverter Valve Function: Initially, check if the valve lever is stuck in the central heating position. Powering down the boiler and observing whether the lever moves back to the hot water position can indicate if the valve is functioning correctly.
  2. Inspecting the Valve and Motor: Remove the control panel and take off the actuator head to check if the valve spindle moves freely. A stuck spindle could indicate a problem with the valve itself.
  3. Evaluating the Synchron Motor and Gears: If the spindle moves freely, the issue might lie with the Synchron motor or the gears underneath it. Worn gears or a malfunctioning motor can prevent the valve from operating correctly.

Solutions for Diverter Valve Issues

  1. Replacing the Actuator or Valve Assembly: If the problem lies in the actuator gears, you may need to replace either the complete actuator or just the pinion and quadrant unit, depending on the extent of the wear.
  2. Considering a New Diverter Valve Assembly: In some cases, replacing the entire diverter valve assembly might be more cost-effective than just replacing individual components. It’s important to match the replacement parts to the boiler model.
  3. Addressing Stiffness in the Actuator Assembly: If the actuator assembly is stiff, lubricating the gearbox underneath the motor might help. However, if this doesn’t resolve the issue, replacing the actuator assembly might be necessary.

Tips for Successful Repair

  1. Referencing the Correct Parts: Ensure you have the correct reference numbers for replacement parts. For example, a common reference for the Worcester Greenstar diverter valve actuator is Honeywell V4044F1109.
  2. Professional Assessment: If you’re unsure about the specific issue or the repair process, seeking professional help is advisable. A certified technician can accurately diagnose and fix the problem.
  3. Regular Maintenance: Regularly checking and maintaining the diverter valve and other boiler components can prevent future issues and prolong the life of the boiler.


Diverter valve issues in Worcester Greenstar boilers, particularly the failure of hot water delivery while the central heating system works fine, are usually fixable with the right approach. Understanding the mechanics of the diverter valve, accurately diagnosing the problem, and choosing the appropriate solution, whether it’s replacing the actuator, motor, gears, or the entire valve assembly, can ensure your boiler functions efficiently. Regular maintenance and professional assistance when needed can help avoid such issues in the future, ensuring consistent performance from your Worcester Greenstar boiler.

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