Turn off power to the thermostat and HVAC system at the breaker
Remove the thermostat cover
Check the batteries and replace them if needed
Inspect the wiring for loose, corroded, or disconnected wires
Tighten any loose wire connections
Set the thermostat to heat or cool mode as needed
Raise or lower the temperature setting to trigger the system
Listen for the system to turn on within a few minutes
Use a multimeter to test voltage at the thermostat terminals
Compare the readings to the manufacturer’s specifications
Test continuity across the thermostat terminals if applicable
Check for proper response when adjusting the temperature dial or controls
Verify the thermostat is level if it is a mercury or mechanical type
Clean dust and debris from the thermostat
Replace the thermostat if it does not respond correctly after testing