What does the Glow-worm Easicom E420 fault code mean?
The E420 fault code indicates an open circuit in the central heating (CH) sensor of the Glow-worm Easicom boiler. This typically means that the boiler is unable to read the temperature of the water in the heating system, which can affect its operation.
Common Causes
- Faulty CH Sensor: The sensor itself may be damaged or malfunctioning, leading to an open circuit.
- Wiring Issues: Damaged or loose wiring connections between the sensor and the boiler control board can cause an open circuit.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer to diagnose and repair this issue, as it involves electrical components and safety risks associated with gas appliances.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for this issue is around £150 to £250, which includes the replacement of the CH sensor and any necessary wiring repairs. This cost reflects the typical price for parts and labour in the UK.