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Kohler Command Twin 18HP - not charging #5078059
04/17/19 06:26 PM
04/17/19 06:26 PM
Joined: Mar 2004
Posts: 1,705
Flaherty, KY
92saturnsl2 Offline OP
92saturnsl2  Offline OP

Joined: Mar 2004
Posts: 1,705
Flaherty, KY
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 265k Chevron Delo LE 5w-40
07 Chrysler Pacifica Limited 4.0L 140k Belgian Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5078084
04/17/19 06:53 PM
04/17/19 06:53 PM
Joined: Aug 2003
Posts: 11,464
Buffalo, NY
JTK Offline
JTK  Offline

Joined: Aug 2003
Posts: 11,464
Buffalo, NY
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)
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5078133
04/17/19 07:36 PM
04/17/19 07:36 PM
Joined: Sep 2015
Posts: 1,810
USA
mk378 Offline
mk378  Offline

Joined: Sep 2015
Posts: 1,810
USA
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
04/17/19 09:01 PM
Joined: Mar 2004
Posts: 1,705
Flaherty, KY
92saturnsl2 Offline OP
92saturnsl2  Offline OP

Joined: Mar 2004
Posts: 1,705
Flaherty, KY
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 265k Chevron Delo LE 5w-40
07 Chrysler Pacifica Limited 4.0L 140k Belgian Castrol Edge 0w-30 Euro
Re: Kohler Command Twin 18HP - not charging [Re: 92saturnsl2] #5079273
04/18/19 08:44 PM
04/18/19 08:44 PM
Joined: Apr 2010
Posts: 52
ms
racinjason Offline
racinjason  Offline

Joined: Apr 2010
Posts: 52
ms
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
04/19/19 08:18 AM
Joined: Feb 2003
Posts: 8,291
Jupiter, Florida
Cujet Online content
Cujet  Online Content

Joined: Feb 2003
Posts: 8,291
Jupiter, Florida
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.
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