Captain Bravo

First, full disclosure. I have not had a 3rd gen F body for a long time. I have never posted here, but have read a fair bit over the years. What brings me here today is that I was searching the web for information on a 10SI alternator problem on my 1979 Massey Ferguson 245 diesel tractor. I found this thread that was very helpful, but did not tell me everything that I was trying to learn. If this isn't allowed, I apologize in advance. But I thought the question might have some relevance to other 10SI alternator users based on the thread that I referenced. And honestly I am more interested in learning if a stator or rotor winding that is shorted to ground could cause this problem.

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. Long story short, tractor wiring is very different from a car, and 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 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.

sofakingdom

iTrader: (1)

Sounds like an internal problem in the alt. Loose wire, worn bearings allowing the armature (rotor) to slide forward or rearward enough to touch something it shouldn't, etc. The "exciter" or "field" or "warning light" connection, whatever you want to call that one, goes to the diode trio and then the regulator, so even a short in the diode trio can't blow fuses; and also the armature and then the reg, so the only path for fuse-blowing current would be a shorted armature, which while rare would also probably take out the regulator.

The wiring in a tractor, or generator or pump or boat or any other similar simple setup, isn't all that much different from a car. Just, simpler. Most of the same knowledge applies.

Captain Bravo

sofakingdom, thanks for the reply. I hadn't considered something coming loose inside. A shorted winding was what I was most concerned about. Sounds like I am going to have to tear it down to find out.

Is there a place you recommend for parts?

8t2 z-chev

Check that the plastic bushings that go around some of the screws that mount the regulator and brusholder are intact and correct position

Captain Bravo

8t2 z-chev, thank you. I'll check those too.

sofakingdom

iTrader: (1)

Not really. Get em from wherever is most convenient. Pay more attention to the country of origin of the part than the name on the box or the sign.

Captain Bravo

Understand. Thank you for your help.