Thermostat emits a buzzing or clicking noise from inside the unit when switching the heating on or off.

Safety: Turn off power before opening the thermostat.

Steps:

• Check load rating: Ensure the connected heating load does not exceed the thermostat's rated current. Oversized loads can cause noisy switching and premature failure.
• Tighten mounting: Make sure the thermostat is firmly clipped to the backplate and the backplate is securely fixed to the wall to reduce vibration.
• Inspect relay area: If accessible, check for signs of arcing or heat damage around the relay. If present, replace the thermostat.

Outcome: A soft click is normal; loud buzzing or chattering indicates a problem with the relay or supply voltage and warrants replacement.