Gas and Oil Home Heating Furnaces - Central natural gas furnace problem

I have a Lennox natural gas furnace/AC unit, about six years old, that is not working. When I set the thermostat for heat, the furnace goes through the regular cycles and ignites the burners. About the time the blower should come on the burners go out leaving only the little exhaust fan going. The blower motor never come on. If I set the thermostat for AC the outside condenser fan runs briefly and then stops. Meanwhile there is no activity at the main unit in the AC mode. If I set the thermostat to "fan on" there is no response at the blower. I greatly appreciate any help you can give!!!! :D ,

This doen't appear to be a diys type problem.. Could something as simple as a broken wire or bad tstat.. Or it may be a motor or fan timer board. Might give some thought to calling a lennox dealer. Especially since you said it was a lennox. Difficult for diys'er to buy parts for lennox in my experience.