Thermostat emits a buzzing or clicking noise frequently when controlling heating.

Safety: Isolate power before opening the thermostat.

• Adjust cycle rate: In installer settings, reduce the number of cycles per hour or enable quieter modulating control if supported.
• Check mounting: Ensure the thermostat is firmly mounted and not resonating against a hollow wall or loose backbox.
• Inspect relay: If comfortable, open the casing and gently press on the relay while operating. If noise changes or relay is loose, the PCB may need replacement.
• Consider solid-state model: If noise is unacceptable, replace with an Ariston model using solid-state outputs.