I am new to this site and looking for some help. I live in a rental property and I have gas heat. When I turned the digital thermostat to heat and set the temp (with the fan on AUTO), nothing blew out of the vents (even though the room temp was 65 and the thermostat was set at 72). If I turned the fan ON, it blew out warm air - but it is too expensive to have the fan running all of the time. Now the vents are blowing out warm air on AUTO after the thermostat shows that the heat has been on about 2-3 minutes. Could there be something wrong with the thermostat itself (some sort of relay switch) or a problem with the furnace? The AC/Heat tech that was sent out says there isn't anything wrong, but this is the first time in 3 years of living here that it has performed this way.