If your home uses a furnace to generate heat, it is important to know how to troubleshoot the furnace's thermostat should it malfunction. A thermostat that is not working properly can lead to discomfort for home residents at best and soaring energy costs at worst. Troubleshooting a Lennox thermostat that does not activate the heat when you turn it up takes only a few simple steps.
Reset the thermostat by turning it to the "off" position for 1 to 3 hours. Turn it back on. This simple reset can solve many common thermostat malfunctions. If the thermostat does not return to normal functioning after the reset, some further troubleshooting is required. Some digital Lennox thermostats have a reset button, in which case you can simply depress the button until the screen goes blank.
Check that the furnace is receiving electrical power. If your furnace has an emergency cutoff switch, check it to make sure it is not tripped. Check the furnace's main power switch also. If the switch is not tripped, check the breaker for the furnace's circuit, and turn it back on if it is off.
Check the furnace door to make sure that it is closed. Lennox furnaces will not activate a heat setting with the furnace door open, so close the furnace door if it is open. If the furnace still fails to turn on at this point, contact a Lennox repair technician and have the technician address the issue from here.