It is unlikely you will find a wiring diagram for an old model. It should be a simple wiring where the plug wires split and one goes to a switch and then from the switch a wire goes to the motor. The other plug wire goes to the motor. The unit probably doesn't have a polarized plug, so no need to know which side of the plug wire goes to the switch and which goes to the motor.
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It is unlikely you will find a wiring diagram for an old model. It should be a simple wiring where the plug wires split and one goes to a switch and then from the switch a wire goes to the motor. The other plug wire goes to the motor. The unit probably doesn't have a polarized plug, so no need to know which side of the plug wire goes to the switch and which goes to the motor.