john deere 318 battery not recharging

markwettigOctober 2, 2013

My JD 318 is eating batteries. After 15 minutes of run time on a fresh battery the battery light will come on. After 1 hour of run time the battery is down to 60%. Can't find an obvious grounding issue. Any ideas?

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bill_kapaun

Apparently this has the ONAN engine.
It appears there could be a couple different models of this engine installed.
Alternator specifications vary, so if you could provide the specific Model#, ie P-218 etc.

What is the battery voltage BEFORE you start the engine?
What is it at high engine speed?

I may or may not have specs, depending on the specific engine/charging system.

IF the battery voltage is below "normal" at high engine speed, you might want to do a preliminary test of the alternator.

Disconnect the plug to the Voltage regulator.
Measure the AC voltage between the 2 AC leads from the stator at high engine speed.
It's safe to say you need a minimum of 28VAC. Some systems should be 41 VAC.
IF you aren't getting at least 28, the stator is bad. VR may also be bad, but you can't really test it with a bad stator.

    Bookmark   October 2, 2013 at 11:06AM
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markwettig

MOD318X425401 bought in 1987.Battery voltage is 12.49 with engine off. 12.38 at low speed and high speed. 35 VAC at VR with plug pulled and Stator wires still attached.

    Bookmark   October 4, 2013 at 4:41PM
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bill_kapaun

What's the Model# of the ENGINE?
It would be something like-
BF-MS2379B
P218-xxxxxx
etc.
etc.

    Bookmark   October 4, 2013 at 5:33PM
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markwettig

Onan P218G-I / 10462A S# L863158351 One more note: I added a starter solenoid relay 5 years ago.

    Bookmark   October 11, 2013 at 5:04PM
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bill_kapaun

The P series have 3 possible charging systems.
One is a 35 amp and the other two are 20 amp.

Examine the Voltage Regulator-
the 35 AMP VR has the 3 leads centered in the middle.
The 20 amp ones have the 3 leads offset to one end.

Hopefully it's the 35 amp, since the 20 amp ones have different minimum output voltages and I really don't know how to identify one from the other. (spec A & Spec B)

    Bookmark   October 11, 2013 at 8:37PM
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markwettig

Sorry I haven't responded sooner. The VR has 2 leads in the center, one over the other and the third towards the end.

    Bookmark   October 21, 2013 at 6:20PM
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ericwi

You might be able to set up a trickle charger on your John Deere 318, and keep the battery maintained that way. A one amp charger will be sufficient, and the low amp charger is best to avoid over charging, which can also shorten battery life. Two days on a one amp charger should be long enough to get the battery fully charged. Then you can run the tractor for a few hours, likely long enough to get your chores done.

    Bookmark   October 21, 2013 at 7:58PM
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bill_kapaun

"The VR has 2 leads in the center, one over the other and the third towards the end."

That doesn't describe any of the VR's in the ONAN "P" service manual.

It should look similar to the one in the link.

Here is a link that might be useful: Link

This post was edited by bill_kapaun on Mon, Oct 21, 13 at 23:57

    Bookmark   October 21, 2013 at 11:49PM
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