Small Engines (Lawn Mowers, etc.): Battery Discharge, john deere model, rapid reply

Question
QUESTION: I have an older John Deere Model 170 lawn tractor.  The battery recently discharged and was replaced.  The replacement lasted a short period, before fully discharging.  It appears to loose charge during operation, evidenced by loss of power to deck PTO.  Can you help identify suspect part for replacement.  Thanks in advance for your assistance.

ANSWER: There is a diode out.  Trace back from the battery to the engine. one of the wires has a bump in it or goes to a rectifier.  Replace the diode or rectifier.

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QUESTION: Thanks for your rapid reply - it is greatly appreciated.

I have found diodes listed in John Deere Parts Catalog for this model, which are located in a wiring harness associated with the alternator assembly.  Are these diodes consistent with your description, or are your referring to diode located along the battery cable?

Thanks in advance for your reply.

Answer
Yes.  All air cooled small engines produce only AC current.  You need DC to charge a battery or fun accessories clutch, lights, etc.  The diode changes AC in to DC by only permitting current from going both ways.  Current should flow to the battery but not to the stator.  Check the diode before you put it in to  be sure you have it in the right direction.  Use a continuity meter.