1985 310 charges 15 plus volts

[qd-16 15]

This has been driving me nuts!!  Ive read all the post  I can about the dual circuit stator and how to bring the voltage down with additional diode/ rectifiers.

 

I have had up to 5 diodes wired inline trying to reduce voltage and this continuously puts out 15.5 amps!! (original diode tested good with ohm meter)

 

 I have been thru 2 coils and 3 sets of points...the high voltage is ruining them.

 

What I have done:

 

     Removed stator and none of the wires appear to be burn or broken, looks real good...all 6 magnets intact in flywheel.

 

     Removed entire wiring harness and checked for broken wires, found none.

 

     Replaced ignition switch (old one was still good)

 

     Battery is fairly new and test good on battery tester

 

     Cannot get any power out of lighting lead....checked with ohm meter and resistance is 1.6

 

     Checked charging lead of stator with ohm meter (before diode/ rectifier) and resistance is around 2.4

 

 

I don't use this wheel horse much but the problem is getting worse....the last coil / points I put in has about 2-3 hours on them and runs really bad.  My

 

instincts tell me the stator has a problem but I want to be sure before I spend the $ on new.

 

Thanks for any given advice, Al.

 

[bitten 134]

Is this the same 85' 10hp engine that is supposed to be 3 amps?

[Save Old Iron 1,571]

Al,

the advice for adding diodes to the stator output only works if the stator is a DUAL OUTPUT stator. If the tractor you have has a points system, please check to make sure if you have a rectifier / regulator assy on the charge system.

 

Do you have something that looks like this on the tractor ?

 

 

If you do, adding diodes to the stator output WILL NOT resolve your higher than normal charge voltage to the battery.

 

Please confirm you have a rectifier / regulator charge system or a dual stator system (hint - dual stator system usually makes the headlights dim significantly as the speed of the engine decreases).

[qd-16 15]

Does not have a voltage regulator.  This is the 3 amp stator.

[Save Old Iron 1,571]

OK good - lets start with a reality check

 

with your meter on AC VOLTS

 

measure from engine ground to the stator lead BEFORE THE DIODE - let's see what the AC voltage is before the diode.when the engine is run 3/4 to full speed.

 

Also check the AC VOLTS out of the headlight tap of the stator (yellow wire ?) with the engine at full speed - measure engine ground to headlight wires to see if we are getting about 12 - 14 volts AC across the headlights.

[qd-16 15]

AC voltage before diode on charging lead is 90.8

 

AC voltage on headlight tap is 33.7

 

AC voltage at the headlights where the power wire connects is anywhere from .4 to 2.6 approx.

 

measurements taken at 3/4 to full throttle.

[Save Old Iron 1,571]

Something is very wrong here.

 

90 volts AC at the output of the stator is dangerous and we must proceed with appropriate caution.

 

First on order is to verify your AC voltmeter is reading correctly. I would suggest taking the same multimeter on AC volts and CAREFULLY measure the AC voltage at one of your home wall outlets. Please read all the cautions in the meter user manual for measuring high AC voltages. The wall socket AC voltage should measure between 110 to 120 volts AC. This procedure will confirm your multimeter is actually measuring the correct voltage at the stator. Measure from the neutral to hot leads in the wall socket.

 

If you are uncomfortable with measuring potentially lethal voltages present at your wall socket - do not proceed any further and seek professional help with your issue on the tractor.

 

90 volts AC on the stator is quite unbelievable but we must proceed under the assumption that this voltage is indeed present on the stator. For the sake of conversation, if you have 90 volts AC at the stator, I would question if your tractor has the correct stator / flywheel combination.

[qd-16 15]

Ok...with the same volt meter my wall outlet reads 117.3 volts AC.

 

Last night I had my cousin come over with his expensive digital multimeter and he also got similar readings from the stator.

[wheeledhorseman 579]

The stator resistance measurements are both slightly high compared with the Kohler spec for them but meters often struggle with accurate readings at very low ohms - that's my experience anyway.

 

The 90 volts you're picking up is way high but it could be that if, as I suspect you are, using a DVM then it could be picking up spikes when the true RMS volts are actually way lower. I prefer using a good old moving coil meter for this sort of work.

 

So here's a thought to follow before spending out on a new stator. Unregulated charging systems like the 3 amp Kohler are designed to produce about 14 volts when connected to a good battery at the normal max rpm setting controlled by the governor. If the revs go higher than this then the output will rise above 14 volts. What sort of voltage do you get on the battery with the throttle backed off a bit to reduce the rpm? If it falls to the more normal 14 volts then maybe the governor setting is out and your engine is turning too fast.

 

Just a thought.

 

Andy

 

Andy

[Save Old Iron 1,571]

I'm convinced your meter is reading properly. Personally, I have never seen a stator produce that kind of voltage unless it was used as a "charge coil" for an electronic ignition system like the older Teckie engines.

 

It may be time to get eyes on the coil to see if it looks like the right stator for the application. Do you have the ability to take a pic or two ?  I don't think I have an actual image of of what a 3 amp stator should look like for your wheel horse.

 

One other thought crossed my mind. When you are measuring the voltages on the two stator outputs, you are measuring with one lead of the multimeter attached to a chassis ground ? right ? 

 

I'm still amazed at 33 volts on the headlight tap. As Andy mentioned above, there will be some effect on the output voltage by having a battery connected vs not connected to the charge lead of the stator, but 33 volts to headlights is off the charts high.

 

Lets get a look at the stator and maybe the magnets in the flywheel.

[wheeledhorseman 579]

Point taken Chuck - just wanted to establish how far out we are here (as have no experience of measurements taken from these)

 

Here's the only pic I can find - so no prizes for guessing who has one up for sale at present on a well known auction site not to be mentioned here.

 

 

I'm guessing the six coils are the lighting and the four coils are charging. Not sure how the charge coils are configured but certainly on the side in view two tails are earthed.  Possibly there another pair earthed on the other side or maybe  pairs of coils are in series but either way it's possible for a poor earth here to result in a kind of series arrangement that would result in higher volt output but a very strange waveform.

 

Given that the headlamp circuit doen't light the bulbs either despite the voltage reading then maybe its the stator frame thats not earthing to the engine as a result of corrosion and all the coils are interacting to give the weird readings.

 

Thoughts?

[Save Old Iron 1,571]

Thanks Andy, that helps.

 

I think we are all in uncharted areas here. The resolution will most likely come from investigation and not anyone's past experience with a similar issue.

 

I hear your point about possibly having the two coils somehow wired in series so their outputs are added together. What incredible luck the two outputs would also be in phase and additive instead of subtractive!  But I guess that depends on magnet arrangement too. All coils may not be energized at the same time to allow phasing to be a player here. But anyway ............

 

Lets say we added both together. Lets say 17 RMS for the charge circuit and 14 RMS for the light circuit. That still only adds up to 32 volts total. Not 90 volts. I remember the screen print Mark took of his stator output on a digital scope showed the stator AC voltage to be fairly sinusoidal in shape so a standard off the shelf digital meter should not have much trouble giving an accurate reading. 

 

I may have a dual output stator stuffed away somewhere where I exchanged it for a standard 15 amp for a neighbor's rebuild. I'll see if I can dig it up later this afternoon.

 

Again, the next best step forward in my opinion is for an eyes on picture of what QD-16's stator and magnet arrangement look like on the tractor.

 

QD - you may want to scan the classified adds for a correct stator. I can't imagine any way for a proper stator to be acting like this. Get us some pics if you can.

[qd-16 15]

Here are some pics.

 

 

 

 

 

 

 

 

[wheeledhorseman 579]

A couple of points that may help with this mystery - firstly, according to the Kohler fault finding guide for the 3 amp charging system disconnected from the battery is that as long as the output at 3000 rpm is '28 volts or more' then the stator is okay.

 

They don't give the reading for the lighting circuit but I'd put money on it possibly being about the same so 33.7 volts measured on the lighting output seems reasonable - the mystery is the 90 volt reading on the charging output - though technically speaking it meets the Kohler spec of 28 volts or higher..

 

I've read elsewhere that these engines do have the full compliment of magnets in the flywheel and that you can 'upgrade' to a 10 amp or 15 amp stator and rectifier regulator to rewire the tractor in the more conventional way. I think then we can discount the flywheel / magnets as a cause.

 

I think I'd begin by checking engine rpm that it's not over the 3000 rpm mark at full throttle - to eliminate it from the overcharging issue if nothing else.

 

Then I'd remove the earth tag to separate it from the stator frame and measure the resistance of each circuit to the tag.

 

.

 

According to Kohler, the resistance from the lead to the diode (stator side) and the earth tag should be 0.7 - 1.3 ohms.  The resistance of the lighting coil lead (yellow) to the tag should be about 0.4 ohms. There should be no continuity (infinite restance) between either of these leads and the stator frame while the earth tag is removed. The above resistance readings should remain constant if the tag (that looks as though it's crimped on) is wiggled a bit.

 

Check the coil resisitance readings (but to the stator frame) once the tag is screwed down to it, and again to the engine block once the stator has been secured to it.

 

If all this checks out then your system has passed the Kohler fault finding guide (assuming 3000 rpm) and it is a real mystery. You are not alone though! In this thread

a guy reported 17 volts at full rpm. The thread goes dead so I don't know if he sorted it or upgraded to an RR based system. Seems to be an issue with these.

 

Andy

 

 

 

[qd-16 15]

Ok, Here are the results from the resistance readings:

 

     With the stator removed from the engine and the grounding tab screw removed ......using the tab as a ground the charging lead is 2.7, lighting lead 2.0

 

     With the stator removed from the engine and the grounding tab screwed down on stator....using the stator frame as a ground....charging lead 2.3, lighting lead 1.6

 

     With the stator on the engine and using the engine block as a ground.....charging lead 2.3, lighting lead 1.7

 

 

I'm fairly confident the motor is not running over governed rpms but I have never tested it with a tachometer....It doesn't sound like it runs any faster than my other horses.

 

Is it possible to still use the same flywheel / magnet set up and "upgrade" to a 10 or 15 amp stator with the addition of a voltage regulator?  This sounds like an appealing option.

 

Thanks, Al

[wheeledhorseman 579]

I can't say yes from experience, but it's what I've read elsewhere and looking a photo I took when I was rebuilding a K301 it looks to mount in exactly the same way.

 

 

 

It might be a good idea to pose the question on the forum to see if anyone's done it but you would of course have to add an RR as well and do a bit of re-wiring. SOI is the master of diagrams for things like this. I'd love to get to the bottom of what's going on here but know from other experience that these unregulated sytems are hit and miss due to simplicity. I have a Tecky 8 HP with one - it's a different system with two diodes and according to the manual if you suffer from over charging, remove one of the diodes which halves the output on the Tecky system. My in-laws have a UK built tractor from the 70s with an unregulated system - there's a switch on the dash to turn the charging off after 5 - 10 mins mowing to prevent the battery being over charged!

 

Andy

[Save Old Iron 1,571]

Conversion to 15 amp wiring is easy

 

 

 

Leads from the 15 amp stator will go directly to the AC terminals on the Rectifier / Regulator (RR)

 

the B+ lead of the RR will be wired directly to the ignition switch "R" terminal.

 

The RR unit will be grounded to the chassis - that's all.

[Save Old Iron 1,571]

@QD

 

Thanks you very much for taking the time to do up the picss of the stator and flywheel - well done.

 

i'm hoping someone more familiar with the "look" of a 3 amp stator and matching flywheel may chime in about if your set looks to be a correct match up. I am not a good WH historian or parts counter guy who can look a part and tell you if there are similar but functionally different 3 amp stators out there.

 

From an electronics standpoint, this is like seeing Bigfoot - actually like seeing an ALBINO BIGFOOT !!!  Unbelievable and never been seen before in my book.

 

Voltage from a stator is dictated by the number of wire wraps on each post and the speed at which the flywheel magnets pass the stator posts.

Amperage from the stator is determined by strength and number of the flywheel magnets.

 

I have seen C series stators put of 50 - 55 volts at full engine speed. The 50 volts is a measurement of the height of the AC voltage from positive peak to negative peak. So there is a 25 volt positive peak and a 25 volt negative peak on the AC waveform. The diode or rectifier / regulator will "chop off" the negative part of the AC wave and leave just a positive pulse out the charge system. So the 50 volt AC wave now becomes half that - a 25 volt positive pule to the regulator. The regulator only allows 14 volts to proceed onto the battery.

 

 

 

In a non regulated system, the stator design engineer intentionally limits the AC voltage output to a point that when "chopped" by a diode, will result in a positive pulse no more than 14 - 16 volts. The regulation of the voltage is actually due to the design of the stator.

 

 

 

If a stator design puts out in excess of 16 volts, this becomes too much stress on the battery. Another diode or two can be inserted in series with the original diode to drop the charge voltage by about 0.7 volts per diode inserted.  In your case, 90 volts AC chopped in half is 45 and inserting 5 diodes would only knock the charge voltage down to 45 - ( 5x 0.7) or about 42 volts DC. No wonder you didn't see a difference when you tried the diode trick.

 

This is certainly the albino Bigfoot, my Moby_Dick white whale. I got to have this one fixed!

 

Let me know if you plan to do the 15 amp conversion, I'll be happy to be of any help I can.

[Save Old Iron 1,571]

@ Andy

 

I don't know if you saw this post Mark contributed regarding the AC waveform from his stator

 

 

 

 

looking back at it - the scope shows 28 volts AC - which when cut in half by the RR unit - will produce around 14+ volts to charge the battery.

[WH nut 553]

_{This is cool stuff, waiting to see the outcome. This is indeed a mystery}

[wheeledhorseman 579]

I don't like mysteries that I can't solve or explain so here's a take on what we have here.

 

All alternators are in a way self-regulating in terms of max current output though this can be tweaked in the design to have an effect on voltage. I first encountered it as a kid with friends when we pulled old dumped motorcycles out of hedges and tried to get them going again. These were the smallest bikes with 50cc single cylinder engines, magneto ignition and lighting coils on a stator much as the 'unregulated' lighting circuit we have here. What we discovered was that if you changed the original headlamp to a higher wattage bulb, it didn't matter how high you reved the engine it wouldn't light at full brightness. The converse was also true, put in a lower wattage bulb and it would burn too brightly at higher revs and inevetably burn out.

 

I didn't know why at the time but it has to do with the 'reactance' of the coils. Put simply, as engine revs increase and the frequency of the AC pulses produced rise then so does the effective resistance of the coils to an alternating current which in turn will limit the current output. This is an efect that doesn't exist with DC. So the lighting coils on these simple systems are designed with a specific current that must be delivered in mind when the gage of wire and number of turns is calculated. Put more powerful headlamp bulb (or bulbs) in the circuit and the current limiting effect means they won't light at full brightness. Put lower wattage bulb (or bulbs) in and the current limiting effect of 'reactance' will not protect them from a higher than normal voltage.

 

Now I suspect that the same 'reactance' effect is put to use in the charging circuit coils on these simple systems that are not designed to be connected to a regulator of any sort beyond a diode to convert AC to DC. There is some support for this theory in the fact that Kohler say the output should be 28 volts or higher. In the case of the engine in question an odd situation exists in that the alternator coils aren't just to replace charge lost from the battery when starting the engine, it has to effectively run the conventional ignition system. So when the coils were designed the reactance of them had to take this into account i.e. perhaps 2.5 amps for the ignition and 0.5 amps to charge the battery (just for illustration). Its a kind of balancing act but the limiting effect was also designed to result in a max voltage of about 14 volts at 3000 rpm.

 

So what could cause this system to start producing more than 14 volts at 3000 rpm - not something you'd expect as faults with the stator coils should generally lower output not increase it. We know that this has been a reported issue on more than one occasion but googling doesn't reveal hundreds of cases. So if it's not the coils then what has changed? I suspect there may be a link here in that if you change the ignition coil from the original to one that has different characteristics and draws less current then you will see the charge voltage rise. It's like putting the lower wattage bulbs in the lighting circuit! Said coil would work perfectly well in a conventional regulated charge situation as is the case for the majority of Kohler engines, but here it will markedly alter the balance of things.

 

There is a second effect that could alter the balance though not to the same extent. When lead-acid batteries age their internal resistance tends to rise. It's an effect that affects some bateries more than others depending on how they've been maitained / how well made they were in the first place. Whilst this effect could be corrected by adding one or two extra diodes into the circuit it will not work for an ignition coil with a very different primary coil resistance to the factory original. Reason: reactance controls current rather than voltage and adding diodes is a voltage based solution.

 

I'm aware of the traces Mark took but these were for a 15 amp alternator where the reactance effect of the coils on a 15 amp stator is such that it limits max current output to about 15 amps. These coils are designed to produce 14 volt half wave via an RR  once the rpm is sufficient and then all the way up to 3000 rpm. Reactance of the coils only comes in to play if you attempt to draw more than 15 amps from it by adding electrical 'attachments' e.g. electric pto, more lights, etc.

 

If my theory holds any weight (and I believe the ignition coil has been changed) then I would add  a lamp as an additional load to the battery and see what happens. E.g. adding a 5 watt 12 volt tail light should reduce the reading on the voltmeter. If it drops but not by enough, try adding another.

 

I can't explain the 90 volt reading but 90 volts at 3 amps would destroy the ignition coil and battery pretty quickly - we know that the actual voltage delivered to the battery in operation is  15 to 16 volts. It's my best shot in attempting to explain what's going on here but certainly unlike the 15 amp stator, the coil design for this stator relies I think on reactance to partially regulate an otherwise unregulated system.

 

Sorry about the length - your thoughts Chuck?

 

Andy