Your furnace and air conditioner should be inspected, cleaned and maintained regularly.    Only a licensed gas fitter should adjust flame and dismantle blower motor for service or repair, however for general inspection and cleaning, a qualified air duct cleaner or filtration and purification specialist may be able do perform the work.  

A basic cleaning of your furnace and AC cooling coil should be done during your air duct cleaning.  Debris from the interior of your ductwork can pass by AC coil and possibly interior furnace compartment depending on method and location of negative air machine / vacuum during cleaning of your air ducts.  To ensure cleanliness, demand your air duct cleaner of choice clean furnace and air conditioning coil properly upon completion of work.