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How do I troubleshoot my Kohler electrical system?

This frequently asked question was posted on the club's Discussion board in the Clubhouse.  Read the response from Al Eden, a long-time Simplicity dealer (see more info).  I've posted it here for easy access and reference.

Subject: Kohler Charging Systems
1/1/2001 8:12:46 PM

Hi, This post will address the problems and theory of the most popular Kohler charging system. I intend to address the Briggs systems soon. They just have so many different versions.

Kohler Charging Systems

The most common Kohler charging system is the 15 amp system, and I believe there are a number of engines out there with 10 amp systems.  The 10 amp system is the same as the 15 amp system except the flywheel has one less magnet in it.  If you are looking at a Kohler flywheel that looks like that it is missing a magnet, it is just a lower current system.

The system is pretty straight forward. There is a flywheel with a ring of magnets on the inside that rotate around a multi-pole stator.  The output of the stator [2 wires] goes to a regulator rectifier and the output of that goes to the battery.

To test the system the first step is to measure the voltage across the battery. The standard voltage source to charge a battery without damage is 14.3 to 15.0 volts DC. This is true in cars, trucks, tractors, anything. Voltages higher than that damage batteries. So you can use this test to check your car charging system as well.  If the system is putting a voltage in this range to the battery it is working.  If the voltage is lower than this several things may be happening.  The system may not have adequate capacity for the load that it is looking at. Examples could be a whole bunch of lights added etc.  But with the lights turned off and just he battery you should see this voltage with this system and the engine wide open. If you only measure 12.0V DC the unit is not charging.  Shut the engine off and go to the voltage regulator. In many of these engines it is now mounted in the fan housing with 2 screws, with the fins inside the fan housing to cool it. In older tractors ex 300 and 400 Acs the regulator was often mounted on the tractor, an aluminum block about 3 by 4 inches with fins sticking up to cool it.  On the regulators there are 3 wires.  Two wires come from the stator and are the same color, one wire is the output to the battery.  If the plug is flat and all three wires are in line as most of the newer ones are, the 2 outside wires are the stator leads and the center is the output.  Some of the older ones the plug is arranged in an L configuration.  I havenít seen one of these for a while and I canít remember which is which, but just look and see which 2 wires come up from the flywheel area, these are the stator leads.

Now that we are at the regulator measure the DC voltage at the Battery Terminal of the regulator. With the key turned on and the engine not running you should see 12.0 VDC. This is the battery voltage.  If not there is a problem between the battery, key switch, ammeter and the regulator, as the battery is not getting connected to the regulator. If you have 12.0Volts DC there, Start the engine, open it wide open and measure the DC voltage on the battery terminal of the regulator.  If you have 14 to 15 VDC you have a bad connection between the battery and the regulator. If only 12 VDC, shut the engine down. Remove the plug from the regulator and start the engine with it running wide open measure the AC [Be sure your meter is on AC VOLTS] voltage coming out of the stator. You should have 28 volts AC or more.  If you do, the regulator is bad.  If not, we will go to the next step.

Shut the engine off.  Take an ohmmeter and measure from each stator lead to ground, it should measure open or infinity. Next measure from one stator lead to the other. This should not be more than a couple of tenths of an ohm. If there is any leakage to ground or the resistance of the stator windings are high or open there are 3 possibilities: (1) The stator is bad; (2) the leads coming from the stator have contacted the flywheel and are either shorting to it, [leakage to ground] or they are cut through, or (3) the stator is open.  If the resistance checks are normal and you didnít have the 28VAC, there are 2 possibilities.  First if you are lucky, the stator may be OK and the magnets may have come loose and are stuck to the stator and the flywheel is turning around them.  If this is the case: BEFORE REMOVING THEM, MARK THEM, SO YOU CAN GET THEM BACK IN THE FLYWHEEL IN THE SAME SEQUENCE AND THE SAME SIDE OUT!!!!!!  You can then remove the glue remnants from the flywheel and noting the stains glue them back in with epoxy glue. YOU MUST REMOVE THE GLUE FROM THE MAGNETS BEFORE RE-INSTALLING THEM, OR YOU WILL NOT HAVE ENOUGH CLEARANCE FOR THE STATOR!!! DO NOT LOOSE YOUR MARKS WHEN DOING THIS!!!  Glue them back in, in the same locations they were.  If this is one of the flywheels that is short a magnet glue them in with the same spacing and the skip as before, use the stain marks in the flywheel.  If they had a skip and you just put them equally spaced around it will not work.  If the stator is undamaged put every thing back together and test her out.  If the magnets physically damaged the stator it will need to be replaced also.

If the flywheel magnets were OK, look at the stator and you may see windings that have been hot and have the insulation burned off.  This may have been caused by something shorting out, causing the stator to overheat.  If the diode bridge in the regulator is shorted out is will cause this also.  Replace the stator and retest the system. If the regulator is shorted you will find it as soon as you recheck the system.  We have a regulator tester [Kohler Special Tool] that will test the regulator, I would expect most Kohler dealers would have this.  It also checks the Tecumseh external regulators.

There are a couple of other Kohler charging systems, one a low current system I have never seen and the other a 30 amp system that uses an external rectifier bridge and a feed back coil in the stator similar to the control system ONAN uses. This is only used on the K500 series engines and they are not used in Simplicity and AC tractors, so I will not go there.  Besides I am a very slow typist.

I hope this is not too confusing, but I think it will cover 99.5% of the problems you will encounter with Kohler charging systems. 

My 2 cents worth and its free so value accordingly. 

Good luck, 




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