How to test turntable motor?

The turntable stopped spinning. Removed old motor, connected voltmeter to leads. When I turn on microwave, it registers 20V, if I set turntable off on panel, then no voltage so it seemed like just a motor. Ordered motor on ********. wb26x10038 GE Microwave Motor Turntable WB26X10038 AP2024962 PS237772.
http://cgi.********.com/ws/eBayISAPI.dll?ViewItem&item=151231557130
Attached to wires and nothing. Vendor shipped me another one and still nothing. How do I make sure it is really the motor and not something else?

That voltage comes from the cooling fan. If you keep the motor plugged in when you measure the voltage, it probably goes to zero.