I have a nordyne intertherm heating and air system in my mobile home. I have attic roof vents which are powered through my circuit breaker box. These vents are not running and the breaker is on and good. There is a air duct (soft) running from my heater up through my ceiling to the attic. Does anyone know if this is all one system or are they two different systems? I am trying to figure out what turns these attic fans on and where to find it. Thanks for any comebacks in advance.

Most powered attic fans are controlled by a thermostat in the attic. If you can find it, if it has one, I would first check the power to it.

You might have the remaining parts of a Coleman Blend Air system. If that is the case the fan was designed to run during the heating season to supply fresh air to the furnace for combustion.