No drain, agitate or spin, lights dim

Hello,

I have an older Kenmore stacking washer/dryer similar to series 90 but I can't be certain which model. It stopped at wash cycle with water in the tub. Going through the cycles by hand it won't spin or drain or agitate. It fills just fine.

After troubleshooting the lid switch, the pump and the drive coupler I ordered a used replacement motor. I connected the new motor to the power while the motor was still outside of the machine, disconnected from the pump and the drive coupling and it moves like 2 degrees but stops. The lights dim and it makes a noise like it's stuck. When I turn the motor by hand it turns freely in both directions. The original motor does the same. This is the part I got - Whirlpool Kenmore Washer Motor 3951550

I suppose it's conceivable that the replacement motor is bad too but is there anything else to check?

Thanks