Rectifier issues

[aloe 24]

I have a 1986 312-A model 21-12KE02 with Engine Model K301S-47829 

The battery isn't getting more than 12 volts charge, so right now have to jump each time I use it.

 

Pretty sure the rectifier is bad, but can't find where the rectifier is located.

 

Is this the right part?  https://www.ebay.com/itm/265400383741?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=265400383741&targetid=1645685073328&device=c&mktype=&googleloc=9004816&poi=&campaignid=16730423415&mkgroupid=135815925780&rlsatarget=pla-1645685073328&abcId=9300841&merchantid=138373634&gclid=Cj0KCQiAg_KbBhDLARIsANx7wAy91Ion03reQG5vaynMWggwq7MdLYNbR8Q3yVaBKnms0QgLp14PFMMaAstSEALw_wcB

[pfrederi 17,741]

I do not think you have a rectifier.  You have the 3 amp unregulated charging system.  What is the voltage with engine running...

[Jeff-C175 7,202]

14 minutes ago, pfrederi said:

do not think you have a rectifier

 

Don't the 3A systems use a diode, and isn't that diode a rectifier Paul?

 

They don't have a REGULATOR though.

 

If there is a diode, look for a 'bump' in the wires coming from the stator. Typically it's covered in tape.

 

If you had the type of regulator in your link, it would be right in your face on the engine shroud. You couldn't miss it.

 

@aloe

Edited November 22, 2022 by Jeff-C175

[Achto 27,609]

1 hour ago, Jeff-C175 said:

Don't the 3A systems use a diode, and isn't that diode a rectifier Paul?

 

Correct, without the diode the system would push AC voltage to the battery.

 

Here is a wire diagram to help you out.

 

 

[peter lena 8,637]

@aloe   https://www.amazon.com/WGGE-WG-026-Pieces-Colors-Alligator/dp/B06XX25HFX/ref=asc_df_B06XX25HFX?a-  have any of these?  clip on one of the rectifier , mount  bolts and the other end to the battery  cable ground bolt . if its a grounding issue  , this will help it work .  engine cooling tins , are frequently rusted , and also poor engine grounding to chassis , with paint / rust will make for a poorly  grounded rectifier point . had the same issue on my horses , the upgraded grounding  stopped my charging issues ,  worth a try , also look over your  , battery cables  , wire connections  , rust / corrosion  , is frequent  , pete  

[953 nut 55,324]

@peter lena, this engine has a single diode rather than a regulator.

I would suggest you check out the white wire from the engine to the "R" terminal on the ignition switch and the wire going from it that goes in under the flywheel cover. The diode itself is a small lump with shrink wrap over it that connects to the white wire. remove the covering so you can inspect the diode for signs of overheating.

The diode should be rated at 50 watts and can be found at https://www.jackssmallengines.com/jacks-parts-lookup/part/kohler/2575531s. The likelihood of a local electronics store having one is slim to none but is worth checking out as you could save some money if they have one.

Edited November 23, 2022 by 953 nut

[Jeff-C175 7,202]

1 hour ago, 953 nut said:

watts

 

Volts I believe,

 

And more than 3 A, at least 4A and better 5.

 

 

Edited November 23, 2022 by Jeff-C175

[8ntruck 7,019]

Have you had the battery checked to know that it is good? 

[953 nut 55,324]

Edited November 25, 2022 by 953 nut

[Jeff-C175 7,202]

57 minutes ago, 953 nut said:

familiar with Ohm's Law 

 

You do know I'm a retired EE, right?

 

Or maybe you 'went there' for the benefit of others?

 

In any case, the amount of power dissipation in a diode is NOT the total voltage * current.

 

It is the Voltage DROP across the diode * current.

 

Diode drop is typically 0.6V so a diode passing 3 A is less than 2 Watts at ANY applied voltage.

 

I'm not sure what you mean by "rejected power".  In the reverse direction there is ZERO power because the diode is not conducting.  

 

 

 

 

Edited November 23, 2022 by Jeff-C175

[aloe 24]

Thanks all for the great advice.  I will get the diode recommended, and see how things go. 

Alan

[Jeff-C175 7,202]

5 minutes ago, aloe said:

Thanks all for the great advice.  I will get the diode recommended, and see how things go. 

Alan

 

Do you own and know how to use a multimeter?

 

If so, TEST THE DIODE before replacing it!

[aloe 24]

yes, I have a multimeter, and can test.  If the Diode is fine, what next? 

[Jeff-C175 7,202]

I would start by going over the thread, answer Paul's question about what voltage is across the battery when the engine is running?

 

Also 8N's question about testing the battery. Are you sure it's good?

 

We need to know more...

 

 

Edited November 23, 2022 by Jeff-C175

[aloe 24]

will check and let you know

[Jeff-C175 7,202]

32 minutes ago, aloe said:

can test

 

Just for reference, here's how, you may already know, but in case not:

 

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes

 

 

[oliver2-44 9,761]

1 hour ago, Jeff-C175 said:

 

You do know I'm a retired EE, right?

Thanks for identifying that Jeff, now we can understand you better. 

 

The EE’s back at work always spoke a different language until we put it in the EE translator

 

Of course they said the same thing about the Mechanical guys. 

[aloe 24]

ok - anwser about the voltage across the battery when the engine is running: 12.8 V

 

Also, don't know why I didn't notice this before, but the PTO light stays on, even with key out...  but that wouldn't be draining a fully charged battery from one day to the next... would it?  

but why would that light stay on... bad switch?

[pfrederi 17,741]

Okay.  Your problem is not the charging system at 12.8 it passes Kohler test. 

Weak battery...parasitic drain....

 

 

[Jeff-C175 7,202]

3 hours ago, aloe said:

when the engine is running: 12.8 V

 

And it drops down to something lower when the engine is stopped?

 

3 hours ago, aloe said:

that wouldn't be draining a fully charged battery from one day to the next... would it?  

 

If the battery is on it's 'last legs', yes, it could.  Depending on the bulb itself, it's even possible that it could draw enough in say 24 hours to seriously deplete a newer battery.

 

I left the dome light on in my Honda overnight and in the morning that battery was low enough that it wouldn't start the car.  Battery was only a few years old.

 

3 hours ago, aloe said:

bad switch?

 

Possibly... more likely a messed up circuit board though.

 

What happens if you 'work' the controls?  move PTO control in/out, flip TEST switch, etc...

 

@aloe

 

 

Edited November 23, 2022 by Jeff-C175

[Jeff-C175 7,202]

I've looked, but can not find.  Is there a schematic of the indicator light PC board on site?

 

@aloe

 

Does your PC board look as messed up as the one in this thread?

 

 

 

 

Edited November 23, 2022 by Jeff-C175

[aloe 24]

The top part where all the wires are coming in doesn't look that bad but I'll have to check out the PC board and see what that looks like

[Jeff-C175 7,202]

@aloe

 

I don't think you've told us, or we asked, is this a manchine that you've had for some time, or is it "new to you" and you're working out the bugs?

 

Oh, and by the way, I don't think that circuit board is needed in order to use the tractor, so you might just try pulling it out and see if the battery holds a charge.

You might find that to be the only issue...

 

While it's nice to have the "Idjit Lites", you can operate without them.

 

 

 

 

Edited November 23, 2022 by Jeff-C175

[gwest_ca-(File Mod) 11,048]

 

[953 nut 55,324]

11 hours ago, Jeff-C175 said:

 

You do know I'm a retired EE, right?          NO

 

Or maybe you 'went there' for the benefit of others?      Any reply I make is intended to help anyone that is searching the subject.

 

In any case, the amount of power dissipation in a diode is NOT the total voltage * current.  The power lost in a diode the half of a cycle that is not passed by the diode, this power is converted to heat.

 

It is the Voltage DROP across the diode * current.  It isn't voltage drop as you would encounter with a resistor, The voltage rejected (not passed) by the diode would be in direct proportion to the current flow.

 

Diode drop is typically 0.6V so a diode passing 3 A is less than 2 Watts at ANY applied voltage.   Diode drop is not the problem with a small diode, it is the heat produced by the half cycle not being passed.

 

I'm not sure what you mean by "rejected power".  In the reverse direction there is ZERO power because the diode is not conducting.  

The half cycle not being passed will produce some heat and a small electronics store 1/4 watt diode would not hold up.