If the thermostat checks out, try turning the fan blades by hand. If they won't turn, the fan may just need to be lubricated withspray lubricant, but it's also possible the attic fan motor has seized, perhaps because of overheating or lack of lubrication. Even if the motor hasn't com...
fan relay broke on the furnace logic board, ordered another board off of eBay and bypassed it to run the fan full time until the part arrived, condenser on the exhaust blower failed, just swapped the condenser and the condensate drain plugged and backed up some water into the fan housing....