John Deere 318 with Honda Engine not charging

Hello Everyone,
I am helping a friend trouble shoot a charging problem with the Honda GX670 replacement engine in his John Deere 318. The alternator is putting out around 28 volts ac, so I think we are ok there, but I am at a loss on what to do next. We don't know which part actually needs to be replaced. The regulator/rectifier is around $150, but the place where he bought the engine from says that it could be a 1” square relay that is causing the problem. Both are very expensive to have sitting around. Currently he is charging the battery with a battery charger which is allowing him to mow his yard before the pto drags all of the juice out of the battery. Any help would be greatly appreciated.
Thanks,
Jack
 
Can you measure any DC voltage at the rectifier/regulator with the engine running? Kohler used that system. Hal
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It sounds like you have a testmeter.

find the wire from the rectifier/regulator to the chassis plug.
disconnect the plug. disconnect the battery negative cable.
set your meter to the ohm scale. put the + meter lead on the pin in the chassis side of the harness plug.
Turn the ignition switch on.
Put the - meter lead on the battery +cable.
Do you have continuity between the pin in the plug and the positive + battery cable?

If you have continuity no more than about 4 ohms, You probably have a bad rectifier.

If you can't find continuity, you have a problem with the chassis wiring.
I am not familiar with Deere electrical (I own a 318 but have not yet had electircal problems) It could very well be whatever relay you mention.
 

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