Question on a Claas round baler net wrap motor.

The Claas 62 baler that I picked up a couple years ago has always had a jury-rigged net wrap system on it and I'd like to get that fixed.  Currently, the system is set up with a manual switch to control the solenoid that diverts hydraulic pressure to either the netwrap system or to the gate cylinders.  However, this jury-rigging eliminated the function of the electric motor which trips the knife, so I'm left stopping the baler and cutting the net wrap by hand.  The original design had a control box that handled this by monitoring a reed swtich that was used to determine the amount of net wrap that had been applied to the bale and then activating the electric motor.  I've checked everything except the control box, the DC motor and the wiring itself.

 

When I started looking at the motor I discovered that it has 4 wires.  I know it is a DC motor and the system runs on 12V from the tractor, but that's about it.  Anyone know a way of testing this motor to make sure it is OK?

Question on a Claas round baler net wrap motor.