Arrived for no heat on gas furnace located in attic. Owner stated that I was 50 F when they arrived this morning but through the day the system began to work again. Began to inspect system and found the the insulation of the blower cabinet had fallen off and was causing airflow restrictions. Secured the insulation and restarted the unit to test and found the inducer motor was running very weak and making loud grinding noise when running. Low voltage fuse popped when system tried to kick into second stage heating. Inducer motor will need replacing to further test system in second stage heating. Recommended flood protection, wet switch, for attic system.