I have seen similar threads on this topic but with some missing info. I have pulled a blower motor, squirl cage and housing out of a furnace. And now want to use it for a exhaust fan in a shop. Some of the wiring was cut (by someone else who pulled the unit out) and the wiring diagram in no longer. The motor is a RMR 240v. 3 speed. Sticker hard to read. The first image is how it is wired. The "red" "blue" and "black" being "low", "medium", "high" connections. The "block" is just a connection block with terminals, wire nuts would have worked just as well. And two brown wires going to the capasitor.
The relay is a 240v. relay with a 24v. coil. Don't want it. But would like to keep the speed switch. As a test I wired it up like the second image. It worked, but...
The motor is listed as a 240v., but the original wiring seams to runs as 120v. The white is labeled as "common". I assumed it is "common neutral". My testing did run although it seamed slow. Since the original wiring was cut, was the original "black" and "red" both supplying 240v. to the motor or is the white (common) be connected as a "white (hot)" . ie. white=120v. and black=120v. or red=120v. totaling 240v. to motor.
If I want to run the motor as a 120v. I would leave as shown in second image and cap the red wire. But if I want to run as a 240v. motor would the white be a common neutral with the black and red connect together? or would the white be a hot lead, black be a hot lead, and red capped or removed?
The speed switch has a blank terminal next to the supply terminal. The black supply to the speed switch can be connected to either terminal and it will still work the same. Or connect the red to the other terminal to get 240v. through the switch.