Danfoss Ally radiator thermostat makes loud grinding or clicking noises during operation.

Safety first: Remove batteries before removing the thermostat from the valve.

Steps:

• Check mounting and adapter: Remove the thermostat and verify that the correct adapter is used and that the valve pin is centered relative to the drive.
• Reinstall and recalibrate: Refit the thermostat carefully and run calibration. Listen for improvement.
• Observe operation: If grinding persists and is clearly from inside the thermostat, the gear train is worn or damaged.
• Replace thermostat: Replace the Danfoss Ally radiator thermostat head; internal gears are not serviceable.