NAA generator

Bernie/MA · Aug 15, 2018

I had the Gen overhauled 2 years ago but still didn"t charge. Just put a new regulator on, still won"t charge but the needle flickers at zero. Cleaned the ground and no change. Would the Gen need work again? Thanks.

Sean in PA · Aug 15, 2018

Have you polarized the generator after having it rebuilt?

Andy Wickiser · Aug 15, 2018

You have to get the multimeter out and start checking things. Are you sure it's not charging, is the battery slowly going flat while operating? What's the battery voltage while the engine is running. Should be 7- 8 Volts or so. You can check if the generator is working by doing the test in the service manual. It involves disconnecting the armature wire, jumpering the armature terminal to the field terminal, inserting an ammeter from armature terminal to disconnected armature wire and seeing if the generator is putting out current. If generator isn't producing then take apart and check connections, commutator, brushes etc. Anyway bottom line is to keep poking around until you find the culprit. Probably should have a service manual and follow the procedures in there.

Jim L WA · Aug 15, 2018

Hi Bernie; You can do a full field test by jumpering from the F terminal to the A terminal on the generator with the tractor running and look at your ammeter. If it shows a charge then the the generator is working. Mine barely shows a charge when running, but when I'm all done, the battery voltage is about 6.5 volts, so It's got to be working.

JMOR · Aug 15, 2018

Both Jim's and Andy's test, it should be pointed out, rely on the VR cut out contacts functioning, and thus are not 'generator only' tests.

souNdguy · Aug 15, 2018

Lets get to basics.

Slip belt off generator. Tighten bracket so Genny is grounded to tractor frame.

Now remove all wires from Genny.

Now jump bat hot to field and armature on Genny.

If she spins good, she SHOULD charge. There are a few situations where she will weakly spin but not charge.

Post back.

If she spins, then you need to hook her belt back up. Put a vom on battery. Once started, jump bat hot to field and armature. She is full fielded, and your vom should show a charge voltage higher than battery nominal. Ie, 6.3v nominal, 7-8 charging, especially if you move the throttle to 66-75%.

If that works, hook her back up, and see what she does with the reg.

If nothing, jump bat and arm/gen at the reg, if still nothing, remove field wire, jump bat hot to Genny field.

That SHOULD provide charge, if your full field test showed charge volts 7-8, etc.

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NAA generator

Bernie/MA

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Sean in PA

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Andy Wickiser

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Jim L WA

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JMOR

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souNdguy

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