Thermostat or valves emit a high‑pitched whining noise when operating.

Safety: Noise alone is not dangerous but may indicate stress on components.

• Confirm source: Place your ear close to each device to identify which one is making the noise.
• Tighten mounting: Ensure the noisy device is firmly mounted and not vibrating against a wall or radiator cover.
• Relocate if possible: Move the thermostat or Relay slightly to reduce resonance with surfaces.
• Monitor behavior: If noise is brief during valve movement, it may be normal. Continuous loud whining suggests a failing component.

Persistent or worsening noise, especially with erratic behavior, indicates the device should be replaced.