Kohler Engine 38 Hp Charging System Diagram

Desember 20, 2021

Topic: Kohler Command 27 Charging Gremlins SOLVED! (Read 3090 times)

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Folks,

The charging system on my Lucas 8/27 with a Kohler Command 27 is not charging the battery, was always weak but now is done.
Diagnosis thus far,

1) Battery is OK, but due for replacement, was fully charged during testing, checked its ability to accept a charge with the wall charger set at 12V/2amp. showed an increase in voltage. Battery at 12.5-12.7 VDC Key on drops voltage approx 0.2-0.3VDC during testing.

2) Regulator/Rectifier, 3 pole, (RR) bench tested with the Kohler special tool. Tests in good condition
3) AC output measured at the stator leads 29VAC, Kohler manual specs 28VAC min.
4) Center pole RR connection which is the charging lead measures battery voltage aprox 12.5VDC with motor running or not with the battery connected.
5) All grounds cleaned to the point of obsession.

Kohler Manual troubleshooting guide:

3a) states if the resistance across the stator leads is infinity ohms, the stator is open, replace stator.
I measure what I believe is infinity, same as when the two meter probes are not touching each other or anything else with the meter set at ohms

3b measure each stator lead if infinity ohms (no continuity) the stator is OK, not shorted to ground.
if resistance (or continuity) is measured the stator leads are shorted to ground. I do not measure/get continuity or resistance, similar to above infinity.

I've pulled the shielding and am down to the flywheel and coils. Before I pull the
balance I wanted to ask,

Can the stator put out voltage as I measured and still not move voltage through the RR to the battery?
Do I have a grounded/shorted stator or something else??

Also, I did find a frayed coil wire which I need to repair.

Any wisdom or past experiences would be greatly appreciated,

mill is all manual with a carb,

Thanks
D

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I would say that if you have at least 28 volts AC across the stator, it is good. Remember proper charging voltage is 13.7 to 14.2 volts DC, so if you rectified that 28 volts AC you would have 14 volts DC. I would replace the regulator/rectifier. Have you got a �known good� you could substitute to confirm this?
You could test for a poor connection in battery voltage circuit from the rectifier to the battery by load testing it. Will that wire power up a headlight bulb?

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"You can't do wrong by doing good"

It's OK to cry.

I never did say goodby to my invisible friend.

Thank you Oliver5262,

I actually have two Reg/Rec both bench tested fine. Neither will convert the 29 VAC to DC,
Kohler changed the grounding scheme on the RR and I adopted that with the new RR I purchased.
Prior to changing the old RR I added a grounding strap to it with no change.

I did a continuity check on the charging wire and the battery voltage at the Reg/Rec B post matches the battery.

D

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Replace your battery, if the regulator bench test fine (both of them) and you have 29VAC your battery is pooch-ed. Grab the one out of your daily driver for giggles and see what transpires.

Or just load test your battery......

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Norwood ML26, Jonsered 2152, Husqvarna 353, 346,555,372,576

Thank you hamish,

I was pushing that back and forth today and probably should have first before pulling the shields.
Even so its only about 30 minutes of work and I did find a chaffed wire that needs repair.

I'll eliminate the battery question.

D

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If the stator is putting out 29VAC there is nothing wrong with it. The vast majority of Kohler charging issues involve grounding of the rectifier. Run a temporary ground wire from the regulator to the negative battery post. Connect a test meter and start the engine. Watch the voltage for 20 seconds or so to see if it graduallyy rises to 14. A bad battery will cause them to raise slowly. If it doesn't show charge either the regulator isn't good or the battery is real bad.

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Peterson JP swing mill
Morbark chipper
Shop built firewood processor
Case W11B
Many chainsaws, axes, hatchets,mauls,
Antique tractors and engines, machine shop,wife, dog,,,,,that's about it.

Folks,
The charging system on my Lucas 8/27 with a Kohler Command 27 is not charging the battery, was always weak but now is done.
Diagnosis thus far,

Kohler Manual troubleshooting guide:

3a) states if the resistance across the stator leads is infinity ohms, the stator is open, replace stator.
I measure what I believe is infinity, same as when the two meter probes are not touching each other or anything else with the meter set at ohms

3b measure each stator lead if infinity ohms (no continuity) the stator is OK, not shorted to ground.
if resistance (or continuity) is measured the stator leads are shorted to ground. I do not measure/get continuity or resistance, similar to above infinity.

Your test in step 3a indicates a bad stator. It is possible you could be using the wrong setting or a bad meter for the test.

IN test 3b you are checking for a stator shorted to ground. Haven't seen a shorted to ground stator produce sufficient voltage.

What I have seen is a stator that makes AC voltage when not connected to the regulator/rectifier, but will not make voltage when connected. Try that.

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Ben cut-wright, thanks for the input

"Your test in step 3a indicates a bad stator. It is possible you could be using the wrong setting or a bad meter for the test." I have a new meter I'm not totally comfortable with. That said I have measured across numerous wires and such with success, it will go auto mode, M or K Ohms.

"IN test 3b you are checking for a stator shorted to ground. Haven't seen a shorted to ground stator produce sufficient voltage." Appears not shorted to Ground

"What I have seen is a stator that makes AC voltage when not connected to the regulator/rectifier, but will not make voltage when connected. Try that."
For my clarity, are you saying measure the AC leads from the back of the connector while connected to the RR with the engine at full speed?
If it does not make voltage is there a repair or do I have to replace the stator?

I appreciate the help thus far,

Thank you

D

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I was wondering if there was a bad stator wire, possibly a mostly broken wire or poor contact at a terminal or in the stator coil itself that when you test ac output you get a reading with a meter but it will not actually get enough output to charge a battery.

I would also would run a temporary ground from RR case to battery negative terminal in case there is a poor engine ground.

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Ben cut-wright, thanks for the input
"Your test in step 3a indicates a bad stator. It is possible you could be using the wrong setting or a bad meter for the test."I have a new meter I'm not totally comfortable with. That said I have measured across numerous wires and such with success, it will go auto mode, M or K Ohms.

"IN test 3b you are checking for a stator shorted to ground. Haven't seen a shorted to ground stator produce sufficient voltage." Appears not shorted to Ground

"What I have seen is a stator that makes AC voltage when not connected to the regulator/rectifier, but will not make voltage when connected. Try that."
For my clarity, are you saying measure the AC leads from the back of the connector while connected to the RR with the engine at full speed?
If it does not make voltage is there a repair or do I have to replace the stator?

I appreciate the help thus far,

Thank you

D

Just a piece of free advice. "Auto ranging" requires a short bit of time in some instances to get an accurate reading. No way to tell you the exact wait time, only auto ranging isn't always instant. That said, if the stator tested infinity and you are comfortable with your methods and tester, the stator is bad.

Yes, test the charging system with all components connected. Specified AC voltage should be available while the circuits are loaded. If this is not the case, the stator or stator wiring is bad.

What wire was frayed?

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Ben C-W

the frayed wire is the brown lead to the coil, you can see it on the right side of the photo

I'll take the recommendations provided and let you all know where I land,

really appreciate the guidance,

D

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What mill model is this engine on?

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Skilled Master Sawyer. "Skilled labour don't come cheap. Cheap labour dont come skilled!
2018 F150 FX4, Husqvarna 340, 2 Logright 36 inch cant hooks and a bunch of stuff I built myself

What mill model is this engine on?

Lucas, 8/27
motor build date 2004

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I haven't done a through read but it sounds to me like the rectifier is bad.

Having 12.5 volts with battery connected doesn't tell much as any half decent battery will show about 12.5 volts just standing. You should show 13.5 to 14.5 idling. Kohler internal alternators are not a real good alternator.

Can you add and external Delco and solve the issue permanently.

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Skilled Master Sawyer. "Skilled labour don't come cheap. Cheap labour dont come skilled!
2018 F150 FX4, Husqvarna 340, 2 Logright 36 inch cant hooks and a bunch of stuff I built myself

Follow-up,

Battery load tested perfect as good as a new one,
Added a second ground wire from the RR to the negative battery ground bolt,
Added a second ground strap from the engine pan to the mill perimeter steel frame.
The motor rides on a rubber isolated steel pan so It ties those together.

New RR full throttle stator connected reads 5.5 VAC at the poles
Disconnected 28.68 VAC.
Old RR about 1.5 VAC at the poles

Interestingly the Clerk at the Parts shop who tested the battery indicated
the system may be voltage dependent and the RR may be managing the
voltage until it see's a low threshold at the battery.
Not certain I believe that

I will try reaching out directly to Kohler to see if they can add some insight,

Thanks for all the input thus far, please don't hesitate to continue to add.
And yes, I repaired/reinsulated the frayed wire
D

Additional comments, I found a youtube channel with Kohler Engine University, seems to
be more comprehensive than the manual.

I'm leaning toward a faulty stator,

D

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Kohler instructions can be misunderstood to mean you can eliminate the stator being faulty if it produces AC when it is disconnected. This is not entirely correct. It does indicate AC voltage is being produced, not that it is proof the stator is good. If you tested your unit correctly, the results you posted here leave little doubt as to the faulty area. Sufficient AC voltage MUST be present when the stator is connected to the reg/rect.

Have you lost faith in your initial continuity tests of the stator? Infinity means the stator is open. You are seeing AC voltage because the magnets induce xAC into all windings, no matter if they have circuit continuity. Sensitive multimeters are able to read this induced voltage. Testing the stator when it is disconnected does not insure it can produce AC power. Your reduced AC test readings when the stator is connected confirm the above.

The AC voltage variance between old and new reg/rect are just that, variances.

Magnets should be checked when you remove the flywheel.

The "clerk" may have been trying to describe the reg/rect's output function. When there is no battery in the circuit, it is normal for the DC terminal to test at a low DC voltage. This output will rise above battery voltage if the charging system is operating properly with the battery in the circuit. All reg/rect do not work this way.

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Hey Ben C-W,

Kohler youtube series matches your comments or vice-versa

Voltage when connected does not meet spec,
Stator resistance measures open. I have rechecked the measurement numerous times

stator needs replacing and make a careful check of the flywheel magnets.

I'll get going on the tear-down in a few days,

thanks
D

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Stator pulled. Oh my!!! the load of sawdust inside the flywheel. Magnets are tight and appear good. The stator has at least 5 poles with pitted corroded windings. ~~I�ll add photos later.~~

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It's amazing how much contamination can pack into that area. Seen it so tightly packed the components were completely hidden from view. Even so, the charging might still work. Some magnets can become detached but still held separate from each other until the contamination is cleaned away.

Corrosive acetic acid in wood severely attacks carbon and alloy steels, moderately attacks copper. Moisture, both in the wood and humidity, greatly increases the corrosive effect. Perfect conditions for corrosive damage when sawing high PH value green logs using water coolant.

Likely some galvanic corrosion happening as well.

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Stator arrived a day early.

Pre-install test, ohms resistance 0.2 right in range,

Install when smooth, found a cheap plastic for-sale sign is exactly 0.012" thick exactly what I needed to set the coil gap.

Battery voltage across the rpm range 14.15 volts.

Main lesson learned, test your stator under load conditions at the regulator/rectifier,
mine provided sufficient voltage when disconnected per one of the Kohler test method.
Connected it made 5.5 volts.

Make sure you test across the the stator leads for ohms resistance as well, if you have 0 you have an issue.

Double check and make your grounds better if needed.

Thank-you to everyone who provided input,

D

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