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Regulator / Rectifier no D/c

#1

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clarkman5000

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


#2

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ILENGINE

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.


#3

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clarkman5000

ILENGINE said:
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.
Click to expand...

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 ..


#4

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ILENGINE

clarkman5000 said:
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 ..
Click to expand...

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.


#5

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clarkman5000

ILENGINE said:
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.
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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..


#6

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ILENGINE

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.


#7

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clarkman5000

ILENGINE said:
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.
Click to expand...

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 ..


#8

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ILENGINE

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.


#9

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bertsmobile1

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


#10

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clarkman5000

bertsmobile1 said:
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
Click to expand...

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..


#11

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clarkman5000

clarkman5000 said:
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..
Click to expand...




Jumped the wire. Same reading . Wondering why my other mower has lots of voltage coming from BOTH a/c terminals and bad motor only from one ?


#12

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Luffydog

If you put the wire on the + side of battery to the center post on the regulator purple wire there is no way you shouldn't have 12 volts dc unless you don't have have a ground on the regulator. So also run a wire from - side of the battery to the regulator that should have you charging if you crank the engine and check the dc voltage then turn engine off and recheck voltage if the same check fuses,wiring,regulator,and if still no charge more than likely your stator has failed but can't rule out the flywheel or possibly both or all the above


#13

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clarkman5000

clarkman5000 said:
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..
Click to expand...

So I jumped the purplewire , Still nothing . I,m going to look at stator seeing that I have only one white wire producing . Maybe I'll find why no juice from battery under the cover .


#14

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bertsmobile1

Are you changing the meter from DC to AC when you check the output from the white wires ?
You should see the 41 volts AC ( actually that is a bit high ) between the two white wires and if the 41V is correct 20.5 V AC between either of them and ground.
If you have left the meter on DC you get the type of readings you are reporting.
If you pull the purple wire off the rectifier it should read the same voltage to ground as the battery reads between the terminals with the key turned on.
IF not you have a bad connection some where.
As already mentioned there was a factory service sheet advising the Purple wire go directly to the red wire and bypass the key switch.
Some manufacturers recommended connecting it directly to the hot terminal on the solenoid by cutting & fitting a ring terminal while others recommended splicing it between the fuse & the B terminal .
When I do one I use another fuse to connect the purple wire to the battery hot terminal cause I like to have things fused.


#15

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clarkman5000

bertsmobile1 said:
Are you changing the meter from DC to AC when you check the output from the white wires ?
You should see the 41 volts AC ( actually that is a bit high ) between the two white wires and if the 41V is correct 20.5 V AC between either of them and ground.
If you have left the meter on DC you get the type of readings you are reporting.
If you pull the purple wire off the rectifier it should read the same voltage to ground as the battery reads between the terminals with the key turned on.
IF not you have a bad connection some where.
As already mentioned there was a factory service sheet advising the Purple wire go directly to the red wire and bypass the key switch.
Some manufacturers recommended connecting it directly to the hot terminal on the solenoid by cutting & fitting a ring terminal while others recommended splicing it between the fuse & the B terminal .
When I do one I use another fuse to connect the purple wire to the battery hot terminal cause I like to have things fused.
Click to expand...

Well this was a learning experience and thank you for all the input and time .. My parts replacing gene was giving me vibes to replace the Key switch in the beginning with the rectifier ( which was bad anyway ) KEY SWITCH .. Narrowed it to that with your help on what and where to test. Almost went to the shop, probably saved $500 .. THANK YOU ALL AGAIN.


#16

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bertsmobile1

Also not all rectifiers are wired the same some are AC-DC-AC while others are AC-AC-DC so make sure you get a Kohler one.
Remember electricity only flows when there is a circuit which means you need a + and a - connection.
Most rectifiers use the case as both a heat sink and the - connection so the outside on the rectifiers must be connected to ground.
Kohler tend to us a flat strap from one of the blower housing bolts to one of the rectifier mounting bolts.
This strap breaks due to vibration so if it is not making a connection then the middle wire can not provide any power.
When I service engine with a rectifier mounted in the plastic blower housing, I make two ground straps and ground the rectifier on both sides to different grounding points.


#17

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clarkman5000

bertsmobile1 said:
Also not all rectifiers are wired the same some are AC-DC-AC while others are AC-AC-DC so make sure you get a Kohler one.
Remember electricity only flows when there is a circuit which means you need a + and a - connection.
Most rectifiers use the case as both a heat sink and the - connection so the outside on the rectifiers must be connected to ground.
Kohler tend to us a flat strap from one of the blower housing bolts to one of the rectifier mounting bolts.
This strap breaks due to vibration so if it is not making a connection then the middle wire can not provide any power.
When I service engine with a rectifier mounted in the plastic blower housing, I make two ground straps and ground the rectifier on both sides to different grounding points.
Click to expand...

Check out my last post .. It was a Bad key switch


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