10SI Alternator Failure Question

There is a 10SI alternator problem on my 1979 Massey Ferguson 245 diesel tractor.

Short back story. Terminal 1 (exciter) is shorted to ground all the time and blowing my main power fuse.

Long back story. The alternator was not charging, so I bought a rebuild kit from Victory Lane on Amazon (yeah, I know). I took it apart, and found that one of the terminals on the voltage regulator was broken. Put it back together with the kit, and it was charging. Then I tried to start it one day, and it wouldn't crank. One of the two fuses was blown. One is for the lights, the other is for the engine (starting circuit, fuel gauge, temp gauge). Traced it to a shorted terminal 1 (exciter) on the (new) voltage regulator. If I unplug the connector on the alternator, everything works except it doesn't charge. If the engine is not running, I can plug it in and it's fine. But as soon as I start it and the oil pressure switch closes and supplies power to the circuit, the fuse blows again. Being diesel, that isn't a problem except that it won't start again until I replace the fuse. And then as soon as the oil pressure switch closes and supplies power to the circuit, the fuse blows again. So for now, I am just leaving the connector off and charging the battery with a charger overnight when it needs it. Obviously not a long term solution. Of course I can take it apart, find out what's wrong, and then order parts. But I can't run the tractor without the alternator in place. And I would like to make an educated guess and buy either a new or rebuilt alternator (more expensive), or a quality rebuild kit (less expensive) first. Then I can get it torn down and re-assembled in one afternoon so I am not without the tractor.

Question. Does anyone know how likely is it that this is just a bad voltage regulator and not an indication of a shorted stator or rotor winding?

Thanks in advance for any help.
 
There is a 10SI alternator problem on my 1979 Massey Ferguson 245 diesel tractor.

Short back story. Terminal 1 (exciter) is shorted to ground all the time and blowing my main power fuse.

Long back story. The alternator was not charging, so I bought a rebuild kit from Victory Lane on Amazon (yeah, I know). I took it apart, and found that one of the terminals on the voltage regulator was broken. Put it back together with the kit, and it was charging. Then I tried to start it one day, and it wouldn't crank. One of the two fuses was blown. One is for the lights, the other is for the engine (starting circuit, fuel gauge, temp gauge). Traced it to a shorted terminal 1 (exciter) on the (new) voltage regulator. If I unplug the connector on the alternator, everything works except it doesn't charge. If the engine is not running, I can plug it in and it's fine. But as soon as I start it and the oil pressure switch closes and supplies power to the circuit, the fuse blows again. Being diesel, that isn't a problem except that it won't start again until I replace the fuse. And then as soon as the oil pressure switch closes and supplies power to the circuit, the fuse blows again. So for now, I am just leaving the connector off and charging the battery with a charger overnight when it needs it. Obviously not a long term solution. Of course I can take it apart, find out what's wrong, and then order parts. But I can't run the tractor without the alternator in place. And I would like to make an educated guess and buy either a new or rebuilt alternator (more expensive), or a quality rebuild kit (less expensive) first. Then I can get it torn down and re-assembled in one afternoon so I am not without the tractor.

Question. Does anyone know how likely is it that this is just a bad voltage regulator and not an indication of a shorted stator or rotor winding?

Thanks in advance for any help.
I would lean slightly towards something shorted, but it looks a lot like a 50/50 deal to me. I would very highly consider going the exchange alternator route if I wanted the more certain fix. If you get an exchange from a parts store, they usually have a warranty, and the store will have another on the shelf to minimize downtime. Another, likely less expensive, option is to see if you can get a used one from a local salvage yard.
 

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