Thermostat shows BAT-01 or low power warning; display may dim or reboot intermittently

Safety: Turn off power to the HVAC system before removing the thermostat.

• Check C wire: Confirm a dedicated C wire is connected at both the furnace control board and the thermostat C terminal.
• Tighten terminals: Ensure R and C wires are firmly clamped at the thermostat backplate and furnace board.
• Battery replacement (if applicable): If your Kasa thermostat model includes user-replaceable batteries, open the battery compartment and replace with fresh, high-quality alkaline batteries in the correct orientation.
• Install C-wire adapter: If your system lacks a C wire, install a compatible TP-Link Kasa C-wire adapter kit according to its instructions.
• Test operation: Restore power and observe the display for several minutes. If BAT-01 persists, the thermostat’s power regulation circuit may be faulty and the unit should be replaced.