Small Engines (Lawn Mowers, etc.): Alternator output, john deere 322, battery chargers

Question
QUESTION: Hi,
I have a John Deere garden tractor, model 322, and the battery/charging light is on. The voltage at the battery is about 12.2V when engine running or not. The battery and voltage regulator are new. I found the main chassis ground for the wiring harness and cleaned and reinstalled it. The light is still on. The alternator output is about 30VAC. Does this sound about right? If so, any other suggestions to check or look at?
Thanks,
Charlie

ANSWER: Charlie

I need to know what engine you have in there. Engine alternators put out different voltages according what is running on the system,lights,pto ignition battery chargers. I need to know what kind of engine the model # and the spec or code #

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QUESTION: The John Deere 322 garden tractor was only ever produced with a 3 cyl 18hp Yanmar gas engine, I think it's model 3TN66UJ. Thanks, Charlie

Answer
Charlie

It's possible the regulator is bad, I believe that engine uses a regulator.  You can check by following the wires coming from the engine, the alternator wire, to the key switch.  If you see a retangular or other shaped device that the engine alternator wire go to then that is the regulator.

Can you measure the DC voltage at the battery with the mower running?  Do you have at least 12 volt DC?
The first step in troubleshooting a charging system is to determine if the stator is putting out enough AC voltage. To do this, simply locate the stator leads (usually two wires together in the same harness coming out from beneath the flywheel or out of the alternator), run the engine at full throttle, disconnect the stator leads from the wiring harness to the battery (which temporarily will not harm the components) and, with your VOA meter set at AC voltage, touch the tester leads to the two stator leads. You should read a relatively high AC voltage--somewhere in the 27 to 45 volts AC (VAC) range. If you have a technical manual available for your machine, check the specification in it or call your dealer to see what it should be. If this test is good, then your stator should be okay.
Let me know about the regulator and voltage.