Thermostat display is completely blank and unresponsive.

Safety: No mains voltage is involved in these steps.

• Install fresh batteries: Remove existing AA batteries and replace them with new alkaline AA cells, ensuring correct polarity.
• Clean contacts: Inspect the battery compartment for corrosion. Clean gently with a cotton swab and isopropyl alcohol, then let dry.
• Check for physical damage: Look for cracks or signs of water damage on the thermostat housing.
• Test after reset: Remove one battery for 30 seconds, reinsert, and wait up to 2 minutes for the display to light.

If the display remains blank with known good batteries and clean contacts, the thermostat’s internal electronics are likely faulty and the unit should be replaced.