What does the Glow-worm Ultimate F87 fault code mean?
The F87 fault code indicates a problem with the domestic hot water (DHW) thermistor, which is responsible for measuring the temperature of the water. This alert suggests that the thermistor may be faulty or there is a wiring issue affecting its operation.
Common Causes
- Faulty Thermistor: The thermistor itself may have failed, leading to incorrect temperature readings.
- Wiring Issues: Damaged or loose wiring connections to the thermistor can disrupt its functionality and trigger the fault code.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer to diagnose and repair this issue, as it involves gas and electrical components that can be hazardous if handled improperly.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for replacing a faulty DHW thermistor on a Glow-worm Ultimate boiler is around £120. This includes the cost of the part and labour, reflecting the typical pricing for such repairs in the UK.