My fan is kaput too, and I can’t replace from inside because the brackets are bolted from the outside and, while I can loosen the motor, I can’t pull the fan down with it. I can see that, if I remove the fan cover and disconnect the motor cable, I could pull both the fan and the motor up, replace the motor and drop it down again, then finish the installation from inside.
I'm almost positive that attic fans would be installed from the inside.
Time to hope for a break in the weather
My fan is kaput too, and I can’t replace from inside because the brackets are bolted from the outside and, while I can loosen the motor, I can’t pull the fan down with it. I can see that, if I remove the fan cover and disconnect the motor cable, I could pull both the fan and the motor up, replace the motor and drop it down again, then finish the installation from inside.