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Thanks bug,
The 2 black plastic connectors are for thermal sensor and brush wear indicator (bwi). Do not use those for now.

On the 4 power terminals, the two in the steel frame are S1 & S2 for series field coils, or F1 & F2 if shunt (or separately excited, SepEx) field coils have been used. The two power terminals on the commutator end head (ceh) casting are A1 & A2, for the armature (through the brushes). You appear to have wired it as a series wound motor for the test, like A1 to battery, A2 to S1, S2 to other battery terminal.

From looking closely at the photo in post 1, I suspect this is a SepEx wound motor. Series wound field coils typically consist of few turns (like 8 to 12) of rectangular cross section varnished copper ribbon on these type of motors. The photo shows a relatively large gauge round magnet wire used for the coils, perhaps like 50 or more turns per coil. Resistance for the set of 4 field coils measured between the two S or F terminals would be extremely low for series wound coils, like 0.010 ohm. For the SepEx coils, more like 1 to 10 ohms, typically. It is difficult to get accurate readings from a multimeter, likely impossible for less than a half ohm.

Usually for a shunt motor, the field voltage equals the armature voltage so A1 to S1 to battery and A2 to S2 to other battery terminal. For series motors the armature current and field current are the same, and voltages are quite different, wiring covered previously. The SepEx is somewhere in-between. Using 12V for a no-load test on a 36/48V motor, if SepEx, try the shunt connection scheme. If you're using a battery, monitor and record the voltage at the motor terminals. Getting power (current) to the field and having a very low armature voltage could cause the lock you describe. You could try a separate battery for the field and for the armature.

Also, the photos show pretty bad contamination of oil, water, battery acid, and ? The field coils look to me as though they've been too hot for too long. There could be insulation damage causing shorts and/or grounds. It could certainly use professional TLC.

Now.... Is it worth it? I really don't think this is a straight-forward series wound motor. Probably a SepEx, but who knows for sure, maybe some kind of "special", or even a hack. It does look like a GE. Maybe a motor rebuild shop could install a replacement series coil set. I kinda doubt it.

Your donor car looks pretty nice. Consider getting a different motor for it. I am curious about the one you have. Get anywhere with it, please post.



{edit} I forgot to mention that finding a suitable controller for a SepEx motor capable of EV voltage and power is difficult to say the least. Check that out before putting a lot of effort/expense into the motor if it is actually a SepEx.
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