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Discussion Starter · #1 ·
Dear Sirs,

I have a John Deere GT 235 that does not seem to charge the battery, I assumed the battery was getting old so I hook up trickle charger when it is in the shed and it starts fine, and if I shut it off within 30 minutes it will restart, but not after that. I decided to try to resolve it today, so I got out the multi-meter to do some troubleshooting. The first thing I noticed is that the battery reads 18.5 volts after I take the trickle charger off. I thought maybe the trickle charger was bad but it reads 14.5 volts when plugged in and not charging anything so that seems about right. When I start the mower the voltage drops to about 16.5, so it seems I have a bad battery, but before I get a new one, what can I do to determine the root cause, does it seem the voltage regulator is bad and that should be changed out as well?

Thanks,

Scott
 

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Hi, first off that voltage on that battery is WAY off! Way too high, dangerous really. Is this trickle charger old? Also your meter may be wrong. Battery voltage when engine running should be 13-14.5 v tops.
 

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Discussion Starter · #3 ·
You are correct, the meter was way off! After I took the first readings and made the entry above I noticed the battery light on the multi-meter came on, got a different meter and now the readings are where I would expect for the battery (14.3v). What seems to be the issue is the AC voltage coming out of the mower, it is only at 13.2VAC, so it seems I should start by replacing the stator to get that up to the expected value of around 26 or so, correct?

Thanks,

Scott
 

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Stator AC output varies by model and charging current capacity. Is this a Briggs or Kawasaki engine? How old is the battery?

I take it you do not see any increase in DC voltage on the battery from when the engine is off to when it is running? Should be around 12-12.8Vdc +/- engine off and like Eric said higher around 13.8Vdc+/- running. But that varies too depending on state of discharge and condition of the battery. Main thing to look for is the voltage increase with the engine running compared to being off.
 

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Discussion Starter · #5 ·
The battery is three years old. It has the Briggs engine with the five wire voltage regulator. The trickle charger (unloaded) reads 13.9 volts, the battery which has been on the charger for a couple days also reads 13.9 (with the charger disconnected), when I start the mower it drops to about 13.6 or so.
 

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The higher voltage reading after taking the battery off of the charger is normal. It's called a surface charge, and should level off after you put a load on the battery.
Make sure you don't have a parasitic draw. Turn off the ignition. Disconnect the positive battery cable. Turn your multimeter to amps or use a test light. Connect your positive lead to the positive battery post and your negative lead to the positive battery cable. There should be zero amps and a test light should not light up. If there is any current flowing something is draining your battery.
I'm pretty sure your regulator converts ac to dc and it regulates the amperage that is sent to the battery rather than voltage. I'm not sure of the specs... Also in order to get accurate readings from the stator you'll need a tach to make sure the engine is spinning at 3600 rpm.
 

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Discussion Starter · #7 ·
I just checked for a parasitic draw and there is none. The voltage still drops ~0.2 volts when the mower is running (13.8 with the engine off, 13.6 when running). I cranked it up to full speed and checked the voltage from the stator and it came up with about 28.5V.

I have the five wire regulator, two wires are the input from the stator and there are three output wires. With the engine running and the stator wire plugged in, two of the wires read 0 volts and one was about .3 volts, that does not seem correct, it seems that one of the wires should be higher than the battery voltage to charge it, or am I mistaken?
 

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Sounding more like the regulator is the problem. We have pdf file on Briggs alternators in our reference library:

http://www.mylawnmowerforum.com/for...riggs-stratton-alternator-specifications.html

The red wire is your charging voltage output, orange and brown wires are for an indicator light according to page 47-48 of the above pdf. The regulator might shutdown it's output when disconnected from the battery. I believe some do that as circuit protection. But you should measure higher voltage approx 14Vdc there when running full throttle and connected to the battery.

(I looked up GT235 on John Deere parts. Then electrical section for the Briggs engine. They show three different regulators that were used in them. A three wire, five wire, and they don't list what the third one was. But for the five wire they list the engine code 350777-1154-E1. So looking that engine model up on repair clinic they give the OEM (Briggs #) of the regulator as #808877. I then searched the above pdf for that number.)

Here's another pdf I just uploaded tonight that I forgot I had. It has some good information on the different types and how they work too.

http://www.mylawnmowerforum.com/for...r-replacement-troubleshooting.html#post352762
 

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Discussion Starter · #9 ·
Mark,

Thank you for the information. I can verify that the regulator is the Briggs OEM #808877.

So does the fact that the voltage drops when the mower is running indicate that the regulator is not working, i.e., the measurement I take across the battery when it is running would be the same I would get if I measured from ground to the red wire coming out of the regulator?

Since I confirmed that the AC voltage from the stator is what it should be, I guess my question is, what procedure could I use to show definitively that the regulator is bad and that it is not some other problem?

Thanks,

Scott
 

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Thinking more about it there is one thing that bugs me and that is the reading your getting on the output of the regulator namely the red wire. I believe it should be tied direct to the positive lead of the battery, possibly via a fuse. Even if the regulator was not putting out charging voltage I would think you should still see battery voltage there. It would not increase with the engine running but would instead slowly drop especially if you turned on the headlights.

So in other words I wonder if you could have an open circuit between the regulator and the battery and the regulator is going into a shutdown mode? Another possibility could be the regulator has a short between one of the output wires and ground and has opened a fuse or fusible link someplace between it and the battery.

I've been trying to find a circuit diagram of exactly how Deere has it wired to confirm these thoughts. As you can see the engine manufacture diagrams are pretty generic and don't show everything that is going on in the circuit. But so far not having any luck finding a model specific diagram. :dunno:
 
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