Hi All. Got a hold of a 1654 engine that had a bad e-unit and was rewired to go just forward.'the problem it has is that after running for a couple of minute it starts to smoke and the field windings get very hot.
Is this symptoms of a bad field or is it a symptoms of bad wiring?
I include a pic showing the wiring basically it’s one field end to ground and the other field end to the other brush to power.
If it is a bad field what are the remedies?
I think you might be looking at something that killed an e-unit…
You can test the field with a multimeter; get the coil ‘resistance’ and also check from field terminals to ground for a partial short. Someone here will give you the correct figure for a good field winding, and should be able to tell you if rewinding the coil is a practical repair for you.
Welcome aboard Flatcar! 
Hello,
I’m trying to look closely at your picture, but it almost looks to be wired “ parallel “. You would want it to be wired”series”. Let me see if I can explain this clearly: you would want the power from the collector to go to one brush, from the other brush to one end of the field, the other end of the field to frame ground. Some engines were wired a little differently, but it needs to pass through each element one time, like a chain.
I don’t know if that is clear enough. But I suspect it is mis wired.
Paul
From what it appears, the brush on the left has the brown wire from the collector and the field. You should disconnect the yellow wire from the left brush and tie it to frame ground. Hopefully,that’s it!
Paul
Great info!
Also, remember that the “ground” mentioned in the diagram is just the motor frame, since the unit is grounded through the wheels to the outside rails. You won’t see anything else other than that.
Paul
As a note: reversing the direction of the motor at the brushes does NOT imply that the field is switched at the same time, as you might inadvertently try to do if you used the ‘forward-only’ circuit as a guide. The field is supplied from the drums on the E-unit and is ‘always on’ while the fingers rotate to choose direction between forward and reverse. A ‘reversing switch’ alone would only involve the two leads to the brushes.
See that what is confusing one of the brushes is grounded so how should the field be wired?
so maybe one end of the field to hot and the other end to the brush that is not grounded?
Hey that worked, the engine now run fine in forward and no more field winding wanting to imitate a smoke unit 
So I guess the symptoms was bad wiring and not a bad field.Yay… fixed.
Thanks to all for the great input!!!
Glad it worked! I did have 2 late prewar engines that had the brush to ground, but most postwar stuff I’ve worked on has one end of the field to ground. You figured it out, hats off to you!
Paul
