I have an American Standard heating/air unit that is 11 years old. Heating unit is located in attic, air is outside. Problem: First fan kicks on, clearing out CO2. Then I hear the gas light up the unit, then I hear another fan kick on blow the heated air through the ducts to the house. I hear a fan start to stop but it doesn't completely, it starts again and then I hear the swoosh from the gas that has kicked back on again to run a cycle. This will happen in cycles until the house heats completely. Another problem that has happened to day is all of the above is still happening, but it now cools down and blows out cold air, not all the time, but sometimes. I also can turn the thermostat down to 60 and kick the fan off sometimes, but not all the time. I don't know if it's the thermonstat, that is also 11 years. I took off the front today and it is a mercury thermometer. Any troubleshooting advice from you pros to keep me from spending money right before the holidays would be appreciated.

Thanks

I don't think it is the thrmostat. But it is hard for me to say if it is a PC board problem or the draft inducer blower motor is going bad.