blower on high is the classic symptom of the resistor. Either blown or just not installed, same effect. Double check that the connector is well seated on the resistor.
If the fan runs fine on high, I wouldn't normally suspect the blower motor. Could be but seems less likely.
Its theoretically possible its the fan speed switch, you could use the wiring diagram at download/file.php?id=2847
and see if you get a ground on the wires at the blower resistor connector for the various fan speed settings