I woke up this morning to find my heat not working again. I had some issues a couple of weeks ago and the service man said the burners and such were rusty; he gave them a good cleaning. Before he cleaned it, it would buzz and attempt to ignite, but wouldn't and would then shut completely off. This morning, however, there is nothing. When I try to turn it on with the thermostat, there is no buzzing or anything; it's just dead. The fan and air conditioning works. Does this seem like an issue with the furnace or thermostat? I have an outdoor combo unit, so if it's in the unit, it can be fixed from outside and I won't have to take off from work to be here.