I have a concord 80 plus gas furnace and today its been working fine until I noticed it started blowing cool air and it won't turn off just steady stays on even when I set the thermostat to off, it just blows like its about to do something but nothing. Usually when I turn it on it blows for a few seconds first and then the heat come on but now it constantly runs like it have a mind of its on now me my wife and my 3 kids have to all sleep in one room until I figure this out. IS THERE SOMEONE OUT THERE THAT CAN HELP ME??