Heater was not working and then suddenly coming on at 4:00 in morning. Does the lennox heater in my attic have a reset button?? Only cool air coming out now... What can I do? I checked the thermo batteries and the thermo box seem to be working just fine...

Provide more info about the heater (model#, gas/elec. etc.).

It is a gas heater in the attic of home central heat I don't know the model # yet. If I change the filter would that help? I will do this tonight also I will try putting the heater on OFF, waiting 15min and trying it again. With these two things being done I hope it will fix the problem. Can you think of anything else I can do??

If the air filter is clogged, it may cause the high-limit control to cycle the burner off due to overheating. If this occurrs frequently and often enough, it can cause the high-limit control to be stuck in the open position.