Thermostat shows F.02 and boiler does not respond to heat demands

Safety: Isolate boiler power before working on any wiring center or receiver. The thermostat itself is low voltage but may be docked to a mains‑powered backplate.

Steps:

• Remove the thermostat from its backplate and inspect the rear contacts for corrosion or debris. Clean gently with a dry cloth.
• Relocate the thermostat temporarily to a normal room temperature area (around 18–22 °C) away from heat sources and cold drafts. Allow 10–15 minutes to stabilise and see if F.02 clears.
• Perform a factory reset of the thermostat via the settings menu (note that this will erase schedules and Wi‑Fi settings). After reset, reconfigure basic settings and check if the error returns.
• If the thermostat offers a diagnostic screen, compare the displayed room temperature with an accurate thermometer. A reading stuck at a very low or very high value indicates a sensor or PCB fault.

Remedy:

• If F.02 persists in a normal environment after reset, the internal sensor circuit is defective. Replace the thermostat head with a compatible Glow‑worm smart thermostat model.
• After replacement, re‑pair the thermostat with the boiler interface (eBus module or RF receiver) and test heating demand.
• If you are not comfortable with configuration or pairing, contact a Glow‑worm trained technician.