M JD Generator

Just had the generator on my 1950 M rebuilt. Brand new field coils, armature, bearings, bushings, brush holder springs, brushes. Still not charging on tractor. Checked all connections and polorized generator. Using brand new solid state cutout relay. Jumped field to ground and still nothin. Took generator off and benched tested it with jumper cables and it would not spin. The guy said he tested it on a 12 volt machine and it was fine. I was out a lot of money to have this done and it still don"t work. What do y"all think is wrong? I don"t want to take it apart until the guy looks at it.
 
The tractor was originally POSITIVE ground so I wonder if your new sold state cutout (diode) is installed in the right direction???? Some are labeled for Neg or Pos Ground, its simply reversing the leads, one to Battery/Ammeter, the other to the Gennys ARM post.

Isnt your M 6 volt?? you mentioned 12 at the shop??

If you polarize the genny to match your battery (Pos or Neg grnd?? Original was Pos),,,,,,,,Insure diode cutout is wired right (if not swap leads),,,,,,,,Insure wiring is right,,,,,,,,,Dead ground the field,,,,,,,but she dont charge I suspect the genny. See my troubleshooting and its gennyMotor Test.

If the diode cutout is right, it will pass current in the direction out of genny to battery/ammeter but NOT out of battery into genny. An ohmmeter will show near zero ohms in right direction/polarity but near infinity open if reversed.

John T
John Ts Troubleshooting
 
Yes it is 6 volt. I tried the cutout relay in both directions with no change and i did ground the field with no change. The wiring is all new and the generator worked before I took it to be rebuilt but not very good. The guy doesnt have a 6 volt testing machine just 12 volt. I got in contact with him and he said bring it back. Hopefully he can go somewhere and test it on a 6 volt machine.
 
That dont sound right, with case grounded and voltage applied to ARM post (Field case grounded) she ought to spin (armature n brushes ok) then remove FLD grnd she ought to spin faster (fields good)

A genny dont necessarily know its voltage output, the faster it spins and/or the more field current, the more it generates.

John T
 
Take him the cut out along with the genny. My guess is he goofed but it will help to have both. All the 6v testing machine is gonna do is give him the 6v power source to do the test's John T has posted. You can carry your fully charged battery with you & do the same thing. His amp meter to check the output doesn't care what the voltage is. It just reads amps & your's is supposed to be 13 IF he used the same internal parts.
 
I'm really concerned since it failed the motor test when all the internals are brand new. I'm taking it all to the guy tomorrow. We shall see what happens.
 
Took generator to shop after work. He just called and said a screw came loose and he tightened it back down with a new lock washer. Said it topped out at 40 amps. Going to pick it up after work tomorrow.
 
(quoted from post at 00:40:36 02/05/13) Took generator to shop after work. He just called and said a screw came loose and he tightened it back down with a new lock washer. Said it topped out at 40 amps. Going to pick it up after work tomorrow.

Tried the generator again after getting it back from shop. Still wont do anything even after following the troubleshooting tips you have. Took it back off and the battery and hooked it up to do the motor test and it won't do anything.
 
If he got 40 amp's you now have the hottest genny around & I don't see how he pulled that off. Anything over 13 out of an M genny is now a 12v unit.
 
(quoted from post at 06:53:01 02/06/13) If he got 40 amp's you now have the hottest genny around & I don't see how he pulled that off. Anything over 13 out of an M genny is now a 12v unit.
Yeah I watched it pull 40 amps on his test stand. Still wont do nothing on the tractor. I did the motor test with the 6v battery on the tractor and it wouldn't do anything. I hooked it to a 12v battery and tried the test again and it spun great.
 
He converted your genny to 12v. That's why it took a 12v to motor test it. It should still work on your 6v system but I think you will have to use a standard regulator with it. The genny is just putting out amp's. Make a new post to catch his eye and mabie John T can tell you about regulating it.
 
(quoted from post at 15:34:26 02/06/13) He converted your genny to 12v. That's why it took a 12v to motor test it. It should still work on your 6v system but I think you will have to use a standard regulator with it. The genny is just putting out amp's. Make a new post to catch his eye and mabie John T can tell you about regulating it.

The guy didn't say anything about it being converted to 12v but maybe all the new parts he used is 12v and he didn't know. If this is indeed the case can't I install a 12v battery along with a normal regulator? Still won't charge on the tractor though, I'm gonna take it back off and make sure its grounding good where it bolts to tractor.
 
Yes you could. You would also need a ballast resistor or just change the coil to one that doesn't need a ballast resistor. I prefer the latter. New bulb's in the light's as well.
 

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