Display shows 'Lo' or a low‑battery icon; thermostat becomes slow or unresponsive and may lose connection to gateway.

Safety first: Battery replacement is user‑serviceable; avoid mixing old and new batteries.

Steps:

• Replace batteries: Open the battery compartment and replace both batteries with new, high‑quality alkaline AA cells, observing correct polarity.
• Clean contacts: If you see white or green corrosion on the contacts, gently clean them with a cotton swab lightly moistened with isopropyl alcohol. Allow to dry fully before inserting new batteries.
• Reduce unnecessary movement: Avoid constantly changing setpoints by small amounts; use schedules in the Ally app to minimize motor cycles.
• Check operation: After replacement, the thermostat should power up, recalibrate the valve, and reconnect to the Ally Gateway automatically.