Coleman-Mach AC unit - no blower on "low" setting.

Thanks guys and for diagram. I'll check these and fan switch

Here's the wiring for a Blower Motor. Coleman uses FASCO but the concept and wiring would be same for other brands.
It's a Reversible motor so disregard the left half of the diagram above "ROT" and the arrows.
It's also Three-Speed so your LOW wire may be a different color than MED or LOW in this pic. But, you should have continuity between WHT (Common) and... BLK for HIGH, and whatever color is left, probably RED or BLU, but that'll be LOW.
That's all it'll take to test your motor, since you know it already runs on HIGH. That eliminates Capacitor along with BRN and BRN/WHT wires. The GRN/YEL is Ground and should be connected but isn't involved in running the motor.
NONE of all the other wires should have continuity to Ground, but again, your motor's running well on HIGH, so I doubt anything is shorted to ground.

There is only one run capacitor for the fan, and no start assist capacitor like the compressor might have.

A Ducted (with wall thermostat and control board) unit will have one possible set of problems and an Non-Ducted (control knobs on the unit itself) will have another.

The motor is the same. Two speeds and the possibility the LOW winding could be out. Non-Ducted has a simple switch like the old home window units and LOW could have failed. That's the stuff I'm familiar with. Ducted is above my pay grade.

When that happened to mine, it was the the low setting on the fan switch. I pulled it off, got the part number, and got a new one on Ebay... less than 20.00.