I have a 12 years old furnace that has stopped putting out heat. The furnace in the attic is on and there is heat. The exhaust pipe, if that's what it's called, is hot and I can hear the flames. However, the air blowing out of the vents is between cool and warm. I have had the thermostat replaced. Turned off the main power to the furnace and turned it back on after at least 5 minutes. Also turned off the thermostat then put it to 90 degrees and let the furnace run and it's still 60 degrees! By the way I have a gas furnace with electronic ignition. Do I need to call a pro? Thank you in advance.

Before calling somebody, go up to the attic and check the ducts. It sound like you have a major leak. You might also try to look inside the heat exchanger to see if it is blocked and the air is bypassing it.

Are you sure the fan is even turning on, is there very much air forced out of the registers?