My 1983 heil model NUGK075DG01, natural gas, forced air furnace is running but only heats the house to 67 degrees no matter how high I set the temp, the fan continuously runs (in auto on thermostat) and the burner will cycle for 3-4 min. then shut-off for 10 min..
I have powered down and back-on, no change in operation. It is currently 6 degrees outside and my family is tired of being cold, any help would be greatly appreciated.

The flame may be going out on limit (Dirty filter, Clogged "A" coil, Dirty blower wheel, Etc.) or it's possible that the flame sensor or thermocouple may need replacing because it may be telling the furnace to shut down because a flame is not detected. It could also be low gas pressure going to the furnace. I'm leaning toward it's going out on high limit... Check the filter first, then have someone come out and have a look..