Display shows 'Lo' or battery icon flashes and thermostat or TRV becomes unresponsive.

Safety: No mains voltage is involved, but avoid mixing old and new batteries.

• Replace batteries: Remove the battery cover and replace all cells with new, high-quality alkaline batteries of the specified size (often 2x AA). Observe polarity markings.
• Clean contacts: If there is white or green corrosion on the contacts, gently clean with a cotton swab and a small amount of isopropyl alcohol. Allow to dry fully.
• Check spring tension: Ensure the battery springs are not bent or collapsed. Gently stretch them if needed to ensure firm contact.
• Reinsert and reset: After installing batteries, wait a few seconds for the device to boot. If required, re-pair the device with the gateway or thermostat.