My impression from post #5's squeal and the lower than regular low speed is that the fan is rubbing on something. It is not the easiest job, need to remove the cowling and wiper assembly first, but should only take a couple of hours. The speed controller is under the blower, so there isn't any point to replacing that first, you'll have the blower in your hands before you can touch the controller.

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Gone to the dark side

- Jeff