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Kohler Command Twin 18HP - not charging #5078059 04/17/19 06:26 PM
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92saturnsl2 Offline OP
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I have two lawn tractors, both have Kohler Command Twins, one a 23 horse, the other is a 18.

The 23 horse unit charges fine. Voltage while running hovers right at 14.0V, when I shut the mower down the battery is usually around 12.8V (maybe a bit higher until the surface charge wears off).

On the 18 horse, it either isn't charging or not charging well. I can't recall the battery being drained completely (I usually hook the charger to it occasionally to prevent that), but it does not behave like the other mower. Voltage while running is usually 12.75 volts or so, and when I shut the mower down battery settles in at 12.5. If I hook a charger to it, the battery will accept plenty more charge, so evidently it's not being charged fully. This particular mower has an ammeter, and when the PTO is engaged or headlights on, the needle reads in the negative (discharge) side of the gauge. If both PTO and lights are on, it's substantially in the negative side. If the mower is just idling at high RPM, the gauge will rest just a hair into the positive.

Just for grins, I swapped what looks like a bridge rectifier (mounted on side of block and has three prongs: AC, AC and B+) between the two mowers. No change.

Any ideas how to go about diagnosing this?


1985 F-250HD 7.5L 4x4 135k- Castrol GTX 15w-40
04 Odyssey EX 190k Valv. Durablend 5w-30
96 Maxima GLE 268k Shell Rotella T5 10w-30
07 Chrysler Pacifica Limited 4.0L 140k Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5078084 04/17/19 06:53 PM
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JTK Offline
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How old is the battery on the 18hp?

Last edited by JTK; 04/17/19 06:54 PM.

2017 Ram 1500 4x4, 3.6L.
2016 Nissan Quest SV (Babe magnet IV)
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Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5078133 04/17/19 07:36 PM
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mk378 Offline
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Make sure the rectifier/regulator is grounded (zero volts from the case to battery (-) when running)

The B+ wire should have battery voltage. The two AC wires should have close to zero ohms resistance to each other through the alternator coil, and an AC voltage of about 15-20 volts when running. Unplugged there should be no continuity from the AC wires to ground.

Re: Kohler Command Twin 18HP - not charging [Re: JTK] #5078229 04/17/19 09:01 PM
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92saturnsl2 Offline OP
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Originally Posted by JTK
How old is the battery on the 18hp?


Battery is only a year or so old-- I've swapped it out with another to no effect.


1985 F-250HD 7.5L 4x4 135k- Castrol GTX 15w-40
04 Odyssey EX 190k Valv. Durablend 5w-30
96 Maxima GLE 268k Shell Rotella T5 10w-30
07 Chrysler Pacifica Limited 4.0L 140k Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5079273 04/18/19 08:44 PM
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racinjason Offline
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Doubt it’s the regulator. As everyone said, check for ground at the regulator and 12v at center regulator terminal.

My money is on the magnets have fallen off the flywheel.

One way to check is read the ac voltage on the two stator wires(outside wires on regulator) running full rpm unplugged, should be 28 or more.

Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5079590 04/19/19 08:18 AM
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Cujet Offline
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Many of those regulators are "total loss". In other words, the alternators produce what they can at any given RPM, the regulator rectifies the AC into DC, and shunts to ground, any excess power, maintaining 13.8V on the system.

It's easy enough to measure the coils on the alternator for conductivity and short to ground. It's not so easy to test a regulator. Replacement of the regulator is generally cheap enough to be worth trying.


People who count on their fingers should maintain a discreet silence.
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5113874 05/23/19 07:16 PM
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92saturnsl2 Offline OP
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Swapping regulators between the mowers has not done a thing, so I presume this issue has nothing to do with the regulator.

I checked the AC voltage on the two stator (outside wires on regulator) wires while unplugged and the two machines are quite different.

The working one is 40+ volts. I don't remember what it was exactly because it was a couple weeks ago I checked it, but it was slightly over 40 IIRC.

The one I'm having trouble with, I checked today and is measuring about 15 volts at full RPM. Any ideas?


1985 F-250HD 7.5L 4x4 135k- Castrol GTX 15w-40
04 Odyssey EX 190k Valv. Durablend 5w-30
96 Maxima GLE 268k Shell Rotella T5 10w-30
07 Chrysler Pacifica Limited 4.0L 140k Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5114026 05/23/19 09:43 PM
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meadows Offline
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Check your ground wire, I had no one that was loose and it did all kinds of weird stuff

Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5114659 05/24/19 03:03 PM
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racinjason Offline
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Originally Posted by 92saturnsl2
Swapping regulators between the mowers has not done a thing, so I presume this issue has nothing to do with the regulator.

I checked the AC voltage on the two stator (outside wires on regulator) wires while unplugged and the two machines are quite different.

The working one is 40+ volts. I don't remember what it was exactly because it was a couple weeks ago I checked it, but it was slightly over 40 IIRC.

The one I'm having trouble with, I checked today and is measuring about 15 volts at full RPM. Any ideas?



I already told you what it was.

Re: Kohler Command Twin 18HP - not charging [Re: racinjason] #5114690 05/24/19 03:41 PM
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92saturnsl2 Offline OP
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Originally Posted by racinjason
I already told you what it was.


Congratulations?

Anyone else know how to fix this issue?


1985 F-250HD 7.5L 4x4 135k- Castrol GTX 15w-40
04 Odyssey EX 190k Valv. Durablend 5w-30
96 Maxima GLE 268k Shell Rotella T5 10w-30
07 Chrysler Pacifica Limited 4.0L 140k Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5115133 05/25/19 06:34 AM
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racinjason Offline
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Originally Posted by 92saturnsl2
Originally Posted by racinjason
I already told you what it was.


Congratulations?

Anyone else know how to fix this issue?





Take the flywheel off and see if the magnets are loose. If they aren’t, put a stator on it. 15volts ac output will never charge your battery. If the magnets are loose, put a flywheel on.

I don’t know what else to tell you, it isn’t magically going to start charging. It has to be one of these two problems.

Second time...my money is on the magnets...hopefully they didn’t take out the stator too. I don’t think so because you are getting 15v ac.

Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5115334 05/25/19 11:31 AM
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92saturnsl2 Offline OP
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Actually it did magically start charging yesterday. Looked down while mowing and the ammeter was solidly in the positive (+5) even with the PTO engaged. I had seen this once before and thought it was a fluke.

I ran and got a meter this time and read +13.8v at the battery and 38 volts AC with regulator unplugged at the outside wires.

I shut the engine down and immediately restarted it and was back to 12.5v at the battery and ammeter slightly in the negative with PTO on.


1985 F-250HD 7.5L 4x4 135k- Castrol GTX 15w-40
04 Odyssey EX 190k Valv. Durablend 5w-30
96 Maxima GLE 268k Shell Rotella T5 10w-30
07 Chrysler Pacifica Limited 4.0L 140k Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5115409 05/25/19 01:37 PM
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racinjason Offline
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Lol, never say never I guess.


Either way, it’s gotta be in that area.

Maybe chase the stator wires and make sure they haven’t chaffed?

Pop the flywheel and I think you will find the problem. 15vac means the problem isn’t after that plug(stator). So..


Flywheel magnets
Charging coil(stator)
Stator wires rubbed


Please report back, I’d like to know what it is that makes it randomly charge, but mostly not charge.

Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5115534 05/25/19 03:48 PM
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92saturnsl2 Offline OP
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Ok, the above info is extremely helpful. I need to get my other mower going (changing some deck spindles) and I will tear into this one and see what's going on in/around the flywheel. I looked at all the exposed wires and didn't see anything amiss, but obviously they disappear behind the engine shroud where I can't see.

Have never taken one of these engines down to the flywheel, is this a difficult procedure? I'll probably figure it out once I'm out there looking at it, just curious what the frustration factor is. smile


1985 F-250HD 7.5L 4x4 135k- Castrol GTX 15w-40
04 Odyssey EX 190k Valv. Durablend 5w-30
96 Maxima GLE 268k Shell Rotella T5 10w-30
07 Chrysler Pacifica Limited 4.0L 140k Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5115902 05/25/19 10:47 PM
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racinjason Offline
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I doubt a wire is chaffed, but ya never know.

Take plastic off, remove flywheel bolt. If you have a puller use it. It’s a tapered shaft with a key way. If you don’t, screw the bolt in with about 3/16 gap between it and the flywheel. Put a pry bar under the flywheel and take the “slack” out (crankshaft thrust), then hit the bolt, should pop off.

Oh yea, coils have to come off kohler.

Not to bad a job, just take your time.

What happens is the magnets get rust under them and they come off. Some folks epoxy them back on, most I see are trash.

I did have a zg20 that they were perfect, just not on the flywheel anymore.

I have seen a lot more of that than stator bad. Sometimes the magnets trash the stator.




Reinstall dry, no lube, make sure key is in the crankshaft. I torque it with an impact(3/8 kobalt 24v) but I’m sure there is a spec.

I use a business card to gap the coils, ain’t failed me yet.

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