1988 310-8 Overcharging

[tunahead72 2,424]

I hope you guys can help me understand this…

 

Late last summer I picked up a 1988 310-8 (model 21-10K805, serial no. 27258), with a Kohler Magnum M10 engine (spec. 461521, serial no. 1717303053).  I can tell it hasn't been maintained meticulously, but it runs, drives and mows pretty good, with a few quirks, and I think it will be a keeper if I can get some things worked out.  I've changed the oil, replaced the spark plug and air filter, greased the chassis and steering, made some minor adjustments and repairs, so far so good.  The previous owner bought it at an auction, and put a new battery in it, but didn't do much else that I can see.

 

I used it probably 15-20 hours last fall, with no real problems, until I noticed that the tractor's voltmeter was reading about 18 volts or so.  I shut it down right away, and let it rest for the night.  I checked it the next morning – the battery read about 12.9 volts on my digital test meter at the beginning of the day, after sitting overnight, which seemed unusually high.  I started it up and let it run for just a few minutes, during which time the needle on the voltmeter gradually but quickly increased to the 18 volts I saw the day before.  This matched what I was seeing at the same time on my tester.  I removed the battery and put the tractor to bed for the winter, and it's been sitting in my yard until now.

 

The Toro Demystification Guide says this tractor should have a 15 amp alternator and regulator-rectifier.  That guide and the Kohler service manual both say that the reg-rec is probably faulty, which makes sense to me.

 

I started looking for the reg-rec, and couldn't find one.  There's a cover on the front of the main blower housing, which I removed, but there's nothing directly behind it.  I removed the engine sheet metal to get a better look, still no reg-rec that I can see.  I can see the ignition module, with one frayed white wire (kill wire?) and the wire to the spark plug.

 

And then I found this in our manuals section, which seems to indicate that this tractor might instead have a 3 amp unregulated charging system.  I can't be 100% sure, because my engine serial number doesn't fit into the range described in "about this file", which says "It is possible the early 1988 310-8 model 21-10K805 used the 1987 3 amp unregulated charging system up to Kohler engine serial 1715900013 (1987 production)":

 

Tractor 1988 310-8 Wiring Detailed Rev.pdf - 1985-1990 - RedSquare Wheel Horse Forum

 

Here's what I'm looking at right now:

 

 

 

 

So, my main questions:
•    Is there any reason to believe this tractor doesn't have a 3 amp unregulated charging system?
•    If it does, what could possibly be wrong to cause overcharging, and what do I do about it?

 

[Handy Don 12,239]

You don't show the wire that is coming from behind the flywheel and going to the battery. If there is a regulator to be found, it'll be on that part of the circuit. I may be a small square box. If there is only a little bulge in the wire enclosed in shrink tube or electrical tape, then you have only a diode and, likely, a 3-amp stator as you surmise.

 

This diode-only system is really only a "recharge the battery and maybe some lights" setup and relies on the battery itself to simply not absorb any more juice than it needs. It also assumes that the engine won't run for excessive periods (an ill-defined interval to be sure ) to force-feed the battery and cook it.

 

The other hint is that solid state voltage regulators don't typically fail "high"--they stop charging altogether or get intermittent.

 

My guess is your battery is starting to fail as it tries to get recharged and hence is letting the stator continue to provide high voltage instead of backing down as the battery gets charged.

[squonk 41,162]

First I'd repair that kill wire even though it isn't your problem. I think there is a diode somewhere to change the AC to DC. Fine that diode and test it. and like Don said, your battery may be the culprit. If you have another battery kicking around, Horse it in there and see if the symptom changes. 

[pfrederi 17,741]

If you have something like circled in pics you have a 15 amp regulated system.  if you do not you have the 3 amp

 

The wire form teh engine to teh ignition switch will have a lump in it on teh engine side of the connector plug.  that is the diode that converts AC to DC but it does not change the charge rate

[tunahead72 2,424]

2 hours ago, Handy Don said:

You don't show the wire that is coming from behind the flywheel and going to the battery...

 

...My guess is your battery is starting to fail as it tries to get recharged and hence is letting the stator continue to provide high voltage instead of backing down as the battery gets charged.

 

You're right about the other wire.  I meant to look for it before I closed things up today, but I forgot.  My '86 310-8 also has a 3 amp system, but I've never had to take it apart this far, so I'm not sure exactly what I'm looking for.  Do any of you guys have a photo showing where it's located?  I do have a photo of the connector behind the engine, if I remember correctly the white wire in this photo is the kill wire.  Would the wire with the diode also go into this connector?

 

 

2 hours ago, squonk said:

First I'd repair that kill wire even though it isn't your problem...

 

Will do.

 

It's interesting that both of you guys mentioned a failing battery as a possibility.  I had a brief conversation with Lincoln from A-Z Tractor at the Lebanon show recently, and he suggested the same thing.  I do have another battery that I can try, I'll let you know how that turns out.

 

1 hour ago, pfrederi said:

If you have something like circled in pics you have a 15 amp regulated system.  if you do not you have the 3 amp...

 

That's what I was expecting, but that's not what I have.  I saw something very similar on Lincoln's 312-8 with a Magnum.  Here's what that area looks like on mine:

 

 

Thank you guys!  We're supposed to get rain tomorrow, and the tractor is outside, so I may not be able to get to it until Monday, but I'll keep you posted. 

[WHX?? 48,833]

4 hours ago, tunahead72 said:

think it will be a keeper

Ok Tuna looks like the fellas have got you handled but  I gotta stop ya right there .... I was led to believe they was all keepers!?!?? 

[tunahead72 2,424]

You're right, Jim, WTH was I thinking?!? 

 

[kpinnc 12,113]

I would suggest two things:

 

1: check voltage across the battery with a multimeter. Engine off and running. Don't trust the onboard voltmeter.

 

2: 18vdc won't harm anything short term. My 310-8 climbs to 17vdc right after startup, but dwindles down to about 13-14vdc after a few minutes. If your battery has high resistance, your rectifier will respond accordingly. If it doesn't settle down after 10 minutes running, see if it behaves the same way with another fully charged battery.

[tunahead72 2,424]

21 minutes ago, kpinnc said:

I would suggest two things:

 

1: check voltage across the battery with a multimeter. Engine off and running. Don't trust the onboard voltmeter.

 

2: 18vdc won't harm anything short term. My 310-8 climbs to 17vdc right after startup, but dwindles down to about 13-14vdc after a few minutes. If your battery has high resistance, your rectifier will respond accordingly. If it doesn't settle down after 10 minutes running, see if it behaves the same way with another fully charged battery.

 

1.  Yep, I was using my multimeter to get accurate readings.  The voltmeter on this particular tractor doesn't seem too far off, at least judging by the little bit of observation time I've had with it so far.  But you're right, I generally don't rely on their readings if the numbers matter.

 

2.  Interesting point.  I didn't observe what happened after a long period of time, just after maybe 10-15 minutes of running at full throttle.  The voltage reading was high then, which is why I shut the engine down, but I don't really know what happens after a longer run time.  In any event, I will be trying a different battery, and watching closely.

 

[kpinnc 12,113]

3 minutes ago, tunahead72 said:

In any event, I will be trying a different battery, and watching closely.

 

Another option if you're concerned about the rectifier cooking stuff- use a charger with a loadmeter on it on the lowest 12v amp setting. If you're seeing 12.9v on the battery alone, then the charger shouldn't load up significantly. If it does, your battery has high resistance of some kind.

 

There are battery testers for resistance that use AC to determine it. Most parts houses can test it, but you risk getting a kid who doesn't know what he's doing too. 

 

 

[lynnmor 7,310]

6 hours ago, kpinnc said:

 

There are battery testers for resistance that use AC to determine it. Most parts houses can test it, but you risk getting a kid who doesn't know what he's doing too. 

 

 

I jump started my BIL's car and followed him to Advanced Autoparts.  I asked the kid to give me the voltage so that I could determine if it was OK to leave instead of standing here in the rain, he looked at me like I had two heads.

[tunahead72 2,424]

Just a quick update here....

 

I swapped in another battery, to see what the charging system would do while it was running.  But I couldn't get the engine started, so I started checking out the basics.  I have spark, and fuel is being pumped into the carb, but it won't run.  I sprayed some carb cleaner into the carb throat while my daughter cranked it over, and it will start and run briefly until the cleaner runs out.  So I took the carb off, and I'll clean and rebuild it, and replace all the fuel lines and filter, and maybe the shutoff at the tank as well (one of the fuel lines is dated on my birthday in 1995!).  I'll be back....

 

In the meantime, I thought you'd all get a kick out of this photo, which shows some of what I'm dealing with here.  The throttle shaft on this carb is really loose, so I'll repair that, hopefully better than the last guy.  If you look closely at the bottom of the photo, there's a very similar repair on the fuel pump:

 

 

[Handy Don 12,239]

While I applaud "out of the box" inventiveness, that is just plain "screwy"!

I'm starting to wonder about the rest of the wiring in the start/run circuits, as well.

[WHX?? 48,833]

Me thinks you got screwed when you bought that tractor... 

[tunahead72 2,424]

3 minutes ago, Handy Don said:

...  I'm starting to wonder about the rest of the wiring in the start/run circuits, as well.

 

So am I.  I tend to not mess with wiring until I need to, just because I'm not real experienced/comfortable with it.  Do you see anything in particular in the photos I posted the other day?

 

1 minute ago, WHX?? said:

Me thinks you got screwed when you bought that tractor... 

 

Twice, that I know of. 

 

[WHX?? 48,833]

Yeah know what your saying Ed... last two tractors to come in needed complete wiring jobs. Fortunately for me wiring is my strong suit. About my only one tho! 

[peter lena 8,642]

0-12@tunahead72  noting your charging issue , ever try a solid ground cable from the battery ground cable bolt , behind dash to the rectifier ? route mine down to engine /frame corner , clutch pedal side , from there wit 10 - 12 ga wire to rectifier mount bolts , from there to headlight grounds . that simple solid electrical grounding , stopped my  electrical issues . just a thought , pete

[tunahead72 2,424]

Pete, I'm pretty sure this tractor doesn't have a proper regulator, but your point about adding extra grounds is certainly a good one, it can't hurt to try.

 

[peter lena 8,642]

@tunahead72  since  my grounding hunt started , with a number of other wiring issues .  just made up a  alligator clip  jumper to go from a  solid ground point , to reach all of my ground areas . immediately got response , with action . my rectifier , was not getting a solid ground  , as well as headlights . also detailed every slide on connection , sandpaper male lead , slide in and dielectric grease every female plug in . once I got a solid amp reading , I was hooked . every one of these horses is different , with separate problems. once I  got one horse , correct , did the same to the other 2 . now all solid , instant starts , good charging , replaced a lot of wiring . replaced cracked connections .  hope you find yours , had to get mad at mine , I  was fed up , pete

[Fishroe 261]

Tuna

my 86 414-8 has had that problem since I bought it 8 years ago. It’s erratic. Has a mind of its own. Sometimes it will peg the volt meter and sometimes it’s perfect. Hasn’t caused any battery problems yet. I tried another diode and it didn’t change anything. 

 

[tunahead72 2,424]

That's all really good to know, thanks!

 

I'm still cleaning/rebuilding/repairing my carb, which is why I was able to help you in the other thread you started, it's all fresh in my mind.  Like I said over there, your tractor and mine have got to be cousins. 

 

[Fishroe 261]

We’re you able to get parts for your carb 

[Fishroe 261]

1 hour ago, Fishroe said:

Were you able to get parts for your carb 

 

[tunahead72 2,424]

Yes, for both the Kohler and the Walbro carbs.  I'll be looking at my notes for these rebuilds later today, I'll get back to you.

 

Once I have part numbers, I usually start with OPE Engines (Kohler Engines and Parts Store, OPEengines.com) and SEPW (Small Engine Parts Warehouse - Lawn Mowers, Trimmers, Lawn & Garden Equipment | SEPW).  They have an excellent selection and quick shipping, and their prices are very good.

 

There's also a list of other suppliers here:  3. Parts Suppliers - RedSquare Links - RedSquare Wheel Horse Forum

 

You can also find things on eBay.

 

BUT my highest priority goes to the vendors here on RedSquare:  Vendors - RedSquare Wheel Horse Forum

 

[Fishroe 261]

Ok thanks