Ihave a Heil heat/air gas pack(forced air) unit. It's about 20 years old, but it's been a great one.Everything works fine I tested both the heat and the ac. The unit is in the attice and only came on when the temperature got really hot up there. Understand it could be fan limit control.. but don't know wher it is in the unit... model NUGG075df01

There should be a part identifacion legacy, on the inside of the door,at 20 years old I would start to be concerned,, get someone to check it out ,the heat exchanger for a safety check,they burn out and get full of holes after a while

wmproop is dead on. Get that heat exchanger checked. The life you save may be your own.

wmproop is dead on. Get that heat exchanger checked. The life you save may be your own.

Whaat about adjusting the fan limit switch (currently set to 70)

wmproop is dead on. Get that heat exchanger checked. The life you save may be your own.

What about adjusting the fan limit (currently 70)

Give it a whirl.

xbennett, I am having same issues on same model, how did you fixed your problem? Please advise, did fan limit adjustment fixed problem?