Just in case you haven’t found the blower motor location (or someone in the future looking at this thread) on the 75-91 E-Series vans, it is NOT under the hood.
The blower motor is located inside the cabin, on the passenger side right above the passengers feet, behind a black panel. If the van has a computer, it’s mounted in front of the blower. The C-6 vans and diesels should not have anything in front of the blower location.
Owning an 85 for a decade, I’m 99.99% certain the blower motor is bad. The way the blower is designed, all the air that is moved by the blower is pulled across the motor.
In the trucks, or just about any engine compartment mounted blower, the motor is on one side of the solid mounting plate, and the squirrel cage is on the other side of the plate. There may be a small “hose” that pushes fresh air to the motor, but for the most part, the air being moved into the cabin is not near the motor.
On the 75-91 vans, the motor mount plate is more like an X, with the motor mounted to one side, the wheel on the other, and all the cabin air is pulled across the motor.
We normally had to replace the blower motor once a year, normally in the fall when the ambient temperature got colder. It would start squealing, and then just not work.
I’m not sure in the 92 up vans how it is set up, but in the 20 years Dad had his 94 I don’t remember him having to replace the blower, and they were both daily driven.