Do you hear any noise at all from the motor when gentle/slow speed is selected? If not, disconnect wires from terminals 1 and 3 on back of speed switch and jump those two wires together and try it in spin mode. If it works, replace the speed switch. If it doesn't work and there is no noise from motor, check white wire at harness connector at motor. Look for broken wire or burned/corroded connector pins. Check continuity of white wire from speed switch to motor connector. With motor connector disconnected, you should have continuity between motor terminals where white wire and blue wire connect. If not, motor switch is defective and motor needs to be replaced.

Eric

GE WH12X10053 Switch Rotary - AppliancePartsPros.com