Verify that the Lennox oil furnace is turned "On" if it is not working and reset the circuit breaker if necessary.
Turn up the thermostat if the furnace is not heating as expected or if it has power but does not seem to be working. Wait at least an hour for the temperature to adjust and verify that the registers, vents and grilles on the unit and throughout the home are not blocked by toys, furniture or other objects.
Turn off the furnace if the unit is not heating properly. Slide the filter out of the front of the furnace. Read the side of the filter and replace if the filter is marked "disposable" or wash with warm water and some dishwashing liquid if it is marked "permanent." Rinse well with water and dry completely. Slide it back in to the furnace when dry and restore power.
Relight the furnace if the pilot light has gone out on the unit. Turn the thermostat to the very lowest setting and turn the furnace "Off." Wait a few minutes and then turn the furnace "On." The furnace is equipped with an automatic lighter, so it is not necessary to try to light the pilot manually. Adjust the thermostat to the desired temperature.
Contact a professional service center if the preceding does not resolve the problem.