Charging Problem with JD 318

Anonymous-0 · Dec 17, 2008

I replaced my battery on my JD 318 last week. A voltage test showed that the battery was discharging 12.5 volts, but only the same 12.5 volts when the machine is running at high throttle. A voltage check on the alternator (stator?) wires that lead to the voltage regulator (VR) was 50v AC at high throttle. A voltage check on the voltage regulator clip that connects to a third wire was ~3 v DC, which tells me that the VR might be bad although I just replaced it two years ago. Does this sound like a VR problem or is there a problem with the stator since I"m getting 50 v AC, which appears high? I was told the stator should put out ~30-36 v.

El Toro · Dec 17, 2008

The 50 vac is too high and could be what's damaging the regulator should be around 30 vac. Clean those terminals on the regulator where the wires are connected and see if you get any Dc voltage. Should be around 14.0 volts. You probaly need to replace that stator. Hal

buickanddeere · Dec 17, 2008

At max rpms that stator voltage is fine. It will still have enough voltage to charge at idle.
A shorting out regulator would have too low of voltage.
An open stator would have no voltage.
There are several different rectifiers/regulators out there. A too low current model will rapidly fail.
As previously stated. A good path back to chassis is esential.
Some of those regulators also require thermal grease to conduct heat away from the regulator and into the heat sink.
Charging a completely dead battery a a vehicles/machines charging system is risky.
The charging system if rated for 15amp is really 15 amp intermittant.
The charging system sees a very low battery as a dead short and output current goes to absolute max for an extended period of time.

Bob · Dec 17, 2008

Since you think the 50 Volts AC sounds high, how would you POSSIBLY explain how that could happen... WHAT could possibly make a permanent magnet alternator put out TOO much voltage... the low part of the sunspot cycle disturbing the magnetic flux from the permanent magnets, perhaps?

THINK ABOUT IT!

Jon Hagen · Dec 17, 2008

I just finished repairing the charging system on a 318. The stator winding had the first coil at one end of the stator winding shorted to ground. This shorted coil was in effect bypassing one of the diodes in the regulator and causing a short.
The thing is that the stator still showed good voltage across the stator leads, but connection an ohmmeter from either stator lead to ground showed it to be shorted to ground.
The stator coil that shorted had quite a build up of oily grass clippings, so I suspect that blocked cooling enough to burn up the coil insulation.
Check that out, the stator leads must read no leakage to ground.
Not a real easy job to replace the stator on a 318, you need to remove the engine. That adds a couple hours work to the job.

Charging Problem with JD 318

Anonymous-0

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El Toro

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buickanddeere

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Bob

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Jon Hagen

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