My furnace blower isn't in use any longer, but it has connections for varying speeds, 6, I think. It only uses 1, though. I'm unsure of how it would even be use

My furnace blower isn't in use any longer, but it has connections for varying speeds, 6, I think. It only uses 1, though. I'm unsure of how it would even be used in practice, as it appears it's just various voltages. Ideally furnace blowers would be inverter ran so you could just tell the inverter how fast to run the fan, rather than changing the supply voltage. Mine was a 3.5 ton HVAC, I replaced it with a five head, five and a half ton "mini split"; while the split air has had it's share of issues (like, I got a full refund of the purchase price a few months ago due to manufacturing defects of the copper lines), I prefer having air handling done bear the ceiling and using 20x20x1 inch filters on box fans (or fancy filters if those are your style) on the floor. The mini split has the inverter driven motors everywhere, and is completely silent during normal use. I have two AQM, and occasionally one or the other will register high CO2 or whatever and I will open a couple of windows and run exhaust fans (built in to the home) to cycle the air, it takes about 20 minutes. The main furnace style system did no filtering or air quality management.