Hi there. I have a problem that I haven't quite seen here and I have no idea how to search for it. Here's the deal: I have a gas furnace. I'm trying to save energy, so I got a new thermostat at the beginning of the fall. I set it to 68 when we're awake and in the house, and 60 after 10pm and when we're away.

Well, it heats just fine, but several times a night, even when it's like 65 in the house, it starts blowing out air. Not heat, just cold air (we don't have AC). So it wastes the heat that's built up in the house!

It's set on heat/auto for the fan.

Any ideas what is happening here? Thanks in advance!!

Check the program. Somehow, it could have been programed to do it. If you don't find anything, check with where you bought it or tech service.

Yes - some of those programmable t-stats can be quite complicated. I wonder if maybe it's set to run fan only at a certain temp or time.

Hi there. I have a problem that I haven't quite seen here and I have no idea how to search for it. Here's the deal: I have a gas furnace. I'm trying to save energy, so I got a new thermostat at the beginning of the fall. I set it to 68 when we're awake and in the house, and 60 after 10pm and when we're away.

Well, it heats just fine, but several times a night, even when it's like 65 in the house, it starts blowing out air. Not heat, just cold air (we don't have AC). So it wastes the heat that's built up in the house!

It's set on heat/auto for the fan.

Any ideas what is happening here? Thanks in advance!

I would see if the adaptive recovery option is set on, this overides your specific settings as to the most efficient means to "ramp up" to your desired set point and time. It will adapt over time to start when it decides is most efficient to reach X gegrees at X time. So if you set it for 6 am and at 4 its running that's why.
It could be the temp delays differential if so equipped, if the on temps not high enough the fan can briefly cycle on/off at times, without a definitive diagnostic its impossible to be accurate.