Rebuilt Generator question

Chadd

Member
Ever since our Farmall M generator was rebuilt, it has required higher engine rpm before it would begin charging. Prior to rebuild, it would charge as long as engine rpm remained about 1/8 throttle or so, even with the lights on. Now anytime the throttle is below 1/4-1/2 open, it will drain (severity depending on electrical load). Also, at full throttle, the needle on the ammeter will bounce back and forth between charge and drain with occasional periods where it will settle down at a slight charge. The VR has been replaced, and it still does it. A multimeter shows that the generator charging rate does seemingly randomly bounce around, and not stay at a set value. Does this sound like a ground issue? My continuity tester says about 7 ohms between chassis ground and ammeter, generator to chassis ground, and VR to chassis ground. The battery never goes dead, but I find such large current swings between +-30 amps a little concerning. It goes away below 7/8 throttle or so and shows a slight charge of a few amps.

Thanks.
 
The generator pulley might be adjustable if so a shorter belt, and adjusting the bulley smaller will make it spin faster. The cutout relay in the VR determins when the system begins to charge. When gen output exceeds the bat voltage a given amount it will pull in and begin charging. JimN
 

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