I replaced my OEM blower motor in my 2014 Prius with an aftermarket motor ( I had done the same thing previously with the same brand on a 2010 Prius). The motor works fine, but when it's on its lowest speed it's still blowing a higher volume of air than what my old one did (to the point of being annoying). Any suggestions on what I can do to lower the fan speed even more? Are there other parts that can be replaced that would impact this?
No. Apparently the aftermarket does not have the same turndown ratio. Meaning it can't go as low and maintain enough torque. Actually I am surprised there is an aftermarket Blower Fan Assembly that responds to the one wire comm channel from the AC Amplifier control.
The blower's "one wire comm channel" isn't anything fancy; the control is a pulse train. The lower the duty cycle (that is, the wider the low parts and narrower the high parts of the wave), the faster the spin. Blower motors with that kind of control input aren't so uncommon anymore.