F.24
Vaillant Low Water Content / Pump Fault / Overheat

F.24 error, boiler overheats rapidly after start, then shuts down

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Insufficient water in boiler, Air lock in heat exchanger, Pump not running or running at too low speed, Blocked primary circuit

How to Fix / Troubleshooting

Safety: Overheat conditions can damage the boiler. Turn off power and let the unit cool.

Checks:

  • Verify system pressure is within the recommended range; top up if needed.
  • Bleed air from the boiler and radiators.
  • Confirm the pump is running when there is a heat demand; feel the pump body for vibration and warmth.
  • If the pump is not running, check the electrical connector and fuse (if fitted). Do not work on live circuits unless qualified.
  • Clean any inline strainers or filters on the return to the boiler.

Professional intervention: If the pump is powered but not circulating, or if the primary heat exchanger is suspected blocked, a heating engineer should diagnose and replace the faulty components.

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Repair Difficulty

Hard 4/5

Required Part

Circulation Pump
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