What should I do if my thermostat display is blank or not responding?

If the display is blank, check that the circuit breaker is on and reset if necessary, ensure the power switch at your heating/cooling system is on, make sure the furnace door is closed securely, and if battery-powered, verify that fresh AAA alkaline batteries are correctly installed (see page 20). If keys are not responding, check that the thermostat is not locked (page 25) and ensure heating and cooling temperatures are in acceptable ranges: Heat 40-90°F and Cool 50-99°F.