Heater or A/C won't turn on

• Check for a blown fuse or tripped circuit breaker

• Make sure thermostat is actually set to "heat" or "cool"

• Make sure the fan is set to "Auto"

• Replace the battery in the thermostat, even if the display lights up

• If one will turn on but not the other, troubleshoot that equipment

Thermostat doesn't come on at the right temperature

or

does not turn off at the right temperature

• Mechanical thermostats need to be level to operate correctly, make sure it is level

• Double check that it is programmed correctly

• Make sure that the thermostat is not affected by drafts from vents, windows or other sources

• Replace the battery in the thermostat, even if the display lights up

Thermostat won't retain programmed settings

• Replace the battery in the thermostat, even if the display lights up