Regulator / Rectifier no D/c

clarkman5000

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Kohler 740 … Engine dying battery dead .. Installed new batt.. Ran for a few hours then Died again with 12volts registering . I'm guessing the fuel was being shut off at bowl solenoid.. Jump start , runs for an hour then dies . I install new rectifier and have 41 vac and a .5 vdc.. I put other machines regulator in knowing its ok , same readout..Jump wired rectifier ground , still same readout . New 25 fuse and .5 vdc in and out . Am I not getting proper ac or wrong new rectifier ? looks the same and no #s on old one to go by. What am I missing >>>>>>>>>>>>>Thanks
 

ILENGINE

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Are you getting 12 volts at the battery prong on the rectifier. Without 12v at the regulator it will not close the internal switch to supply power for charging.
 

clarkman5000

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Are you getting 12 volts at the battery prong on the rectifier. Without 12v at the regulator it will not close the internal switch to supply power for charging.

I'm getting .5 at rectifier... It is a new rectifier . I also put a used /working one in . Same thing .5 volts dc....40+ volts ac ..
 

ILENGINE

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I'm getting .5 at rectifier... It is a new rectifier . I also put a used /working one in . Same thing .5 volts dc....40+ volts ac ..

Let me rephrase. Are you getting battery voltage to the B terminal wire (purple wire)in the wiring harness to the regulator. Unless that purple wire has battery voltage input to the regulator you won't get charging output. Try running a temporary wire from the battery terminal of the regulator straight to the positive battery terminal of the battery, and then check voltage.

So if you have the connector at the regulator connected and the engine running, and you set your volt meter to DC and put the red lead to the B terminal of the regulator, and the black lead to ground you should read battery voltage. If you are still getting .5 volts then you need to find out why you don't have power from the battery.
 

clarkman5000

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Let me rephrase. Are you getting battery voltage to the B terminal wire (purple wire)in the wiring harness to the regulator. Unless that purple wire has battery voltage input to the regulator you won't get charging output. Try running a temporary wire from the battery terminal of the regulator straight to the positive battery terminal of the battery, and then check voltage.

So if you have the connector at the regulator connected and the engine running, and you set your volt meter to DC and put the red lead to the B terminal of the regulator, and the black lead to ground you should read battery voltage. If you are still getting .5 volts then you need to find out why you don't have power from the battery.

Thanks for your input .. But I thought the ac voltage went INTO the regulator and the B wire dc went TO the battery and the voltage should be 13+.. I'm 25 % Mechanic !00% parts replacer :) I just discovered that the ac is only coming out of one side of the rectifier .. Thinking now Its under the flywheel my problem .. Maybe the Stator ?I will investigate..
 

ILENGINE

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The AC does go into the regulator, but the B terminal which is the center terminal on most of the Kohler regulators has to have 12v from the battery to close the microswitch inside of the regulator to let the DC out. If the purple wire doesn't have battery power to the regulator the regulator will not output power to the battery.

If you connect a DC volt meter to the purple wire and to either a frame ground or the negative terminal of the battery, what voltage are you reading. Be aware on some mowers the key has to be turned to the run position for it to work, but the purple wire can be wired directly to battery which is the recommended Kohler method anyway. If that wire doesn't read the same as the voltage in the battery, it will not charge the battery.
 

clarkman5000

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The AC does go into the regulator, but the B terminal which is the center terminal on most of the Kohler regulators has to have 12v from the battery to close the microswitch inside of the regulator to let the DC out. If the purple wire doesn't have battery power to the regulator the regulator will not output power to the battery.

If you connect a DC volt meter to the purple wire and to either a frame ground or the negative terminal of the battery, what voltage are you reading. Be aware on some mowers the key has to be turned to the run position for it to work, but the purple wire can be wired directly to battery which is the recommended Kohler method anyway. If that wire doesn't read the same as the voltage in the battery, it will not charge the battery.

So turned key on and got Zero d/c at purple "B" wire at the connector .. and the battery has 12.35 volts in it . Did you see that I have only one a/c side reading voltage while running .. Thanks so much for this help ..
 

ILENGINE

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If you are getting 41 volts AC when you connect an AC volt meter between the two stator wires, then it is fine. Regulator should be fine, and you already checked the regulator ground. The fact that you are not getting battery voltage at the terminal on the end of the purple wire is the reason it won't charge. If not already done, you can connect that purple wire either to the positive post of the battery, or the battery side of the starter solenoid. It will not discharge the battery even if it has constant voltage at the B terminal of the regulator.
 

bertsmobile1

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A little explanation you might find useful.
Electronically permanent magnet alternators & motors are the same thing.
So if you apply voltage to an alternator it will try to spin.
On your mower it can not spin because it is not strong enough to turn the engine over.
Thus the wires get hot and you battery goes flat.
To stop this happening there are electronic switches built into the rectifier/regulator.

Early on mowers used the ignition switch to prevent this happening but running the recharge current through the ignition switch burned the switches out so the switching was built into the regulator
 

clarkman5000

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A little explanation you might find useful.
Electronically permanent magnet alternators & motors are the same thing.
So if you apply voltage to an alternator it will try to spin.
On your mower it can not spin because it is not strong enough to turn the engine over.
Thus the wires get hot and you battery goes flat.
To stop this happening there are electronic switches built into the rectifier/regulator.

Early on mowers used the ignition switch to prevent this happening but running the recharge current through the ignition switch burned the switches out so the switching was built into the regulator

Going to jump purple wire this am and see what ive got. Thanks so much for your advice . Working on equipment for long time and I learn as I go but electricity is sometimes hard for me to wrap my head around . Always try to do my own work on my trucks tractors and lawn equipment always willing to learn from folks like you . Thank you for your time..
 
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