F24
Glow-worm
Low Water Content / Pump or Flow Fault
Boiler displays F24, indicating a rapid temperature rise followed by shutdown.
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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
Airlock in the boiler or pump, Pump not running or incorrectly wired, Blocked primary circuit, Closed isolation valves
How to Fix / Troubleshooting
Safety: Allow the boiler to cool before working on pipework. Isolate the power supply before touching electrical connections.
- Check pressure and top up: Ensure the system pressure is adequate (approximately 1.2–1.5 bar cold).
- Bleed boiler and pump: Some Glow-worm models have manual air vents on the pump or heat exchanger. Carefully vent air with a cloth to catch any expelled water.
- Verify pump operation: On a heat demand, feel the pump body; it should vibrate slightly and become warm. If not, it may be stuck.
- Engineer tasks:
- Check the electrical supply to the pump.
- Free or replace a seized circulation pump.
- Inspect for blockages in the primary circuit or heat exchanger.
Do not run the boiler with known circulation issues; overheating damage can occur.
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Repair Difficulty
Medium
3/5
Required Part
Circulation Pump
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