Tom, to get the motor to run you need to connect power to one brush, connect the other brush to one motor field lead, and connect the other motor field lead to the other power wire. Looking in the cab from the tender what you see is the brush plate. Above the brush plate is the motor field coil. The leads for the field come out on the engineers side. One goes to a terminal on the brush plate, the other goes forward to the e unit. The brush holders are on the lower edge of the brush plate. They each should have a lug that comes to each side of the brush plate. Normally those lugs would be connected to yellow wires that go forward to the e unit.
When connecting the motor to power wires, it does not matter which wire goes to the brush or field. It is AC and the wires have no polarity. They are interchangeable.
Connect one power wire to either brush lug. Use a jumper wire to connect the other brush lug to one of the field leads. Connect the other field lead to the other power wire. The motor should run, but it must have good brushes in it. To reverse the direction reverse the power wire and jumper to the field on the brush lugs.
I would suggest you take the motor out. With all the wires disconnected it only requires removing the two mounting screws on the front. To rewire the loco the motor has to come out as the rear collector terminal is under the drive shaft. With the motor out you can remove the screws that hold the gear unit cover on. This will let you remove the cover , which has the e unit mounted to it. With the cover off , and the gasket if it stays with the frame, you can lift the worm shaft out. The bearings will come with it. Now you can get to the rear collector lug.
This may sound like a lot of work to get to a lug to solder on a new wire, but this gives you access to the interior of the gear box, which is probably full of very old hard grease, which needs to be cleaned out and replaced. With the worm shaft out you can remove, clean and relubricate the bearings on one end of the shaft. To get the bearings off the other end the gear needs to be removed by loosing the set screw and tapping it off. The things that look like washers are actually hardened and ground thrust washers. The side the ball bearings are running against need to continue to be the wear side.
The weak point in this loco is the fiber gear on the end of the worn shaft. It's condition will determine the future of the loco. I have never found any sold as spare parts, but they might be out there somewhere. I also remove the gear on the motor shaft so I can remove the armature from the motor to clean it and get oil in to the front bearing. There is a second bearing on the motor shaft that sits on the commutator. Keep track of that as it needs to go back on. If the set screws in the gears are slotted so they can be removed with a straight blade screw driver, they may break when being removed. Replace them with set screws with a recessed hex drive. That will make life so much easier.
