JD alternator not making currenr

8850dave

Member
I've got a JD 3250 alternator from the early 80's runs good but not putting out any voltage , any ideas what I need to do to get it working again
 
If the unit has simply sat unused for long enough that residual magnetism in the rotating field polepieces has been lost over time it won't generate 'til the field coils have been "flashed". There's several ways to do this, but the simplest and safest is detailed in the quote below.

Some portable alternators have diodes and an electrolytic capacitor that can fail/go bad over time, and the procedure below cannot fix that, but it's simple and costs nothing to try. If it doesn't work, likely something has failed and repairs will be needed.

"Field Flashing of Portable Generators

This tip comes from the Briggs & Stratton Customer Education Department. As an alternative to flashing a rotor winding with a battery applied to the brushes, an electric drill may be used. Follow these steps to flash the generator:
? Plug the electric drill into the generator receptacle. (Cordless drills do not work)

? If the drill is reversible, move the direction switch to the forward position.

? Start the generator

? While depressing the trigger on the drill, spin the drill chuck in reverse direction. This will excite the field and the generator will now produce electricity. If spinning the chuck one direction does not work, try spinning the chuck in the other direction as you may have the reverse switch positioned backwards.
Use caution not to get your hand or other materials caught in the chuck. As soon as the field is excited, the generator will produce power and the drill will turn on.
The reason this works is because the electric motor in the drill will act as a small generator when spun backwards. The magnets in the drill's motor induce a voltage into the motor windings, which is fed back through the trigger, cord and into the generators receptacle. From there it goes into the power winding of the stator. The voltage going through the power winding creates a magnetic field, which is intensified due to the iron core of the stator laminations. The rotor intersects this magnetic field as it is spun past the power winding, thus inducing a voltage in the rotor winding. Once current flow is present in the rotor winding the rotor has been flashed.
If flashing the field does not make the generator work, you may have additional problems, besides a lack of magnetism in the rotor. Further testing will be needed. Hopefully, this will give a simple way to field flash your generator if needed - "
 
Make sure you have 12 volts going to the alternator when you turn on the switch. If it isn't it will not charge. I experienced the same issue with a 2955 and the alternator was not getting 12 volts after turning on the switch. Of course I figured that out after I had installed a new alternator.
 

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