[shorod]

Measure for voltage to the motor from the switch. The switch simply reverses the polarity to the motor, so since the motor works in one direction, the wires have to be good to the motor. And theres a single power and ground feed to the switch so that has to be good as well. That comes pretty close to diagnosing it to the switch since the motor worked when you bench tested it. I'd still like to see you verify with a meter or test light that you are only getting power in the "down" position before suggesting you replace the switch though.

-Rod