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Discussion Starter · #1 ·
On my 58 Country Squire I've had the feeling that the old mechanical voltage regulator for the starter/generator was not working 100% the Ammeter needle would jiggle and at higher engine R's it seemed to stop charging. So I decided to install an electronic generator control / VR I've used these on another B&S with a starter/gen and they work great. Its made for Harley Davidson motorcycles PN is 74504-87, you have to cut the HD 3 prong connector off ( couldn't find one anywhere) an used insulated slip connectors made a mounting bracket to mt it to the side of the trans as I didn't want to fight with the hood at this time will in the fall. Mounted it connected the wires started the engine and happy days it was charging 15 amps on start up dropped back to 5/6 after a less than a minute had 14.6 VDC pull the lights on and the amps went up some and held its a keeper
HPIM1479.JPG HPIM1480.JPG HPIM1481.JPG HPIM1482.JPG HPIM1484.JPG HPIM1486.JPG HPIM1489.JPG
 

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On my 58 Country Squire I've had the feeling that the old mechanical voltage regulator for the starter/generator was not working 100% the Ammeter needle would jiggle and at higher engine R's it seemed to stop charging. So I decided to install an electronic generator control / VR I've used these on another B&S with a starter/gen and they work great. Its made for Harley Davidson motorcycles PN is 74504-87, you have to cut the HD 3 prong connector off ( couldn't find one anywhere) an used insulated slip connectors made a mounting bracket to mt it to the side of the trans as I didn't want to fight with the hood at this time will in the fall. Mounted it connected the wires started the engine and happy days it was charging 15 amps on start up dropped back to 5/6 after a less than a minute had 14.6 VDC pull the lights on and the amps went up some and held its a keeper
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I wonder if that would work on my Cub Cadet 106? How much is that HD part?
 

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Discussion Starter · #3 ·

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Nice upgrade to the electronic unit. Do you have any specs on what the maximum current setting is on those units they will allow a generator to produce before they start regulating the current output?
 

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Discussion Starter · #5 ·
Hi Stew, I think the first one I did a couple of years ago had that information but I can't find where I put it for safe keeping buy I seem to recall 15 amps this new one had nothing with it and I can't find any real answers on the net.
I have a question for you can you tell me why the cheap Tiny Tach copies don't work with the old Kohler cast iron singles the readins are erratic but they seem to work ok on the B&S with magnetos Kohlers have battery ignition
 

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Hi Stew, I think the first one I did a couple of years ago had that information but I can't find where I put it for safe keeping buy I seem to recall 15 amps this new one had nothing with it and I can't find any real answers on the net.
Hi Gary, thanks for the information. Limiting at 15 amps might be a little high for some applications such as my Bolens 1053 which has a -10 - 0 - +10 amp movement of the needle as the ammeter might peg at initial start up. Probably wouldn't hurt the meter but it would be hard to tell the total amount of current the generator would be producing with the meter full scale to verify the current limiting was working ok. According to the Wisconsin manual the amount of current the starter generator on it should put out is 10 amps - for your application where you have a higher reading scale should work ok.

Will think about the Tiny Tach issue and provide a response that may help.
 

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Discussion Starter · #7 ·
Hi Stew you are right at start up it most likely would peg the meter, I noticed mine goes over 10 amp but quicly drops down in less than a minute
 

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Hi Stew you are right at start up it most likely would peg the meter, I noticed mine goes over 10 amp but quicly drops down in less than a minute
Yes - that is how the regulator and generator should work after just starting the engine if the battery is good and everything is working properly. After startup the charging voltage will be low and the current output will be high and it is what needs to be regulated initially so the generator does not get overworked and too hot. Then after about a minute the current demand of the battery usually drops as it gets recharged and the voltage in the charging system rises - the current limiting is no longer required and the regulator then starts to limit the voltage level.
 

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I have a question for you can you tell me why the cheap Tiny Tach copies don't work with the old Kohler cast iron singles the readins are erratic but they seem to work ok on the B&S with magnetos Kohlers have battery ignition
Please note that this is strictly my opinion having been involved with electronics as a hobbyist for many years. I apologize in advance for the wordy response - I will try and answer your question but will have to go into a bit of detail to do so which I will try to keep in simple terms so it is understandable. I am going to assume that the Kohler’s you are referring to have starter / generators or generators to provide current for the charging system. As I am sure you are aware a generator and the associated regulator provide a very “dirty” D.C. current when supplying charging current when the engine is running. The brushes making and breaking contact with the commutator segments on the armature while they transfer several amps of current flow would create a lot of short lived but still very present voltage spikes during a single rotation of the armature. Most volt meters won’t see the spikes but if you viewed it on a scope it might surprise you. Given the pulley ratios between the engine pulley and generator pulley on small engine applications the generator is usually turning at two to three times the engine rpms which creates quite a number of spikes that are part of the D.C. current that is being supplied to the battery and other components in the electrical system at any given minute that the engine is running. Since the voltage level in the charging system is constantly being regulated (quickly rising and falling for fractions of a second as the regulator turns the field current on and off) the D.C. voltage that one normally thinks of in a generator charging system can actually be considered to have a rather high frequency A.C. part attached to it if viewed as a waveform. Since the ignition coil is connected to the charging system with a wire from the ignition switch to the primary side of the coil the wire will act as an antenna to radiate the A.C. portion of that voltage along with any momentary spikes the same way that high voltage hydro wires along a road could create a buzzing effect on an old CB radio years ago. The windings in the ignition coil will tend to amplify any A.C. signal presented to it as it is in effect a low voltage to high voltage transformer. The amplified A.C. voltage will probably not be enough to jump the spark plug gap to create an engine misfire but it can and probably is providing enough of a signal to trigger the sensitive tach pick up wire as a spark plug firing signal and result in erratic readings being displayed on the tach.

In contrast a magneto system is isolated from the charging system so that any voltage spikes / A.C. created from the charging system are not induced into the ignition coil or spark plug wire and the tach pick up wire sees a pretty clean signal (in comparison) as the spark plug fires. The Tiny Tach copies may not have as good a filtering inside the units to try and differentiate what is “electrical noise” and what is a true spark plug being fired signal to provide an accurate rpm display.

Now that hopefully I have explained the problems that may be creating the erratic readings let me make a few suggestions that may help if you have not already tried them. You could temporarily remove the field wire from the generator and see if the tach now works properly with the engine running. This should help you determine if the charging system noise is creating the erratic display or if it is stray R.F.I. being generated by the ignition system You could also try installing an electrolytic capacitor at the positive terminal of the ignition coil – I am assuming that the charging system is 12 volt negative ground and that the coil is triggered by a contact set connected to the negative terminal of the coil. A 100 uF 25 volt capacitor should help to remove any A.C. ripple before it enters the ignition coil windings – make sure you connect the positive lead of the capacitor to the positive terminal on the coil and the negative lead of the capacitor to ground – keep the leads as short as possible. You could also try winding the antenna wire that goes around the spark plug wire in the reverse direction to what it is now or moving the antenna wire location closer to the spark plug. You could also install a slit piece of vacuum / heater hose over the spark plug wire and then wrap the pickup wire over it – this would move the pickup wire further away from the center of the plug wire so that any signal generated from the spark plug wire isn’t as strong to the pickup wire and then wrap a piece of aluminum foil over top of the pickup wire to shield it from any stray R.F.I. generated in the vicinity of the ignition coil. Place a piece of electrical tape over the end of the pickup wire so that the tin foil does not contact it - you can secure the foil with a tie wrap if it cures the problem. You could also run the complete wire from the tach inside tinfoil or a piece of metal tubing (brake or fuel line) so that the wire is completely shielded from any R.F.I. if you think that is what is creating the erratic readings.

Hope this helps
 

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Discussion Starter · #10 ·
Hi Stew good information I thanks for taking the time to reply, but I should have said the Kohler's I was referring to have the stator/alternator with a rectifier voltage regulator, I might add that trying to use a digital VOM to check regulator voltage is the same impossible thus I aways use my analog meters although a digital VOM will work if you are approx 4/5 ft away from the engine
 

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Hi Stew good information I thanks for taking the time to reply, but I should have said the Kohler's I was referring to have the stator/alternator with a rectifier voltage regulator, I might add that trying to use a digital VOM to check regulator voltage is the same impossible thus I aways use my analog meters although a digital VOM will work if you are approx 4/5 ft away from the engine
Hi Gary,

If the engine is using a stator to provide power for the charging circuit I would still be inclined to think that there is an A.C. signal that is radiating through the wiring going to the ignition coil as well as the possibility of R.F.I. being generated that the tach antenna wire is picking up thinking that it is a spark plug firing. This is just my opinion - I will try and explain why – again I apologize for the in depth wordy post.

Unlike a vehicle charging system equipped with an alternator where the field current is turned on and off to control output and voltage level a small engine stator relies on permanent magnets passing over fixed coils wired together to generate an A.C. current that is produced within the stator windings. The frequency of the A.C. current being produced if the engine is running at 3000 rpm will be a minimum of 3000 (rpm) / 60 (to get seconds) or 50 cycles per second – this frequency will vary as the engine speed changes. The actual frequency may be much higher depending on the number of magnets and coils and how they are wired and interact with each other – would need to use a meter that can read frequency or a scope to know for sure. Even at 50 cycles per second (or 16.6 cycles / second at 1000 rpm (50/3 = 16.6)) this would be enough to create a good buzzing sound on an AM radio if the antenna was close enough – again I will reference back to the hydro lines which carry A.C. with a frequency of 60 cycles per second and a CB radio. The voltage level on the A.C. side of the wiring coming from the stator to the regulator will be approximately 25 – 30 volts if the stator is functioning properly which will allow the A.C. signal to radiate and transfer along the stator wires to the voltage regulator. Remember that the stator is always producing voltage and current from engine start up until it is turned off – unlike a vehicle where the fields are being rapidly turned on and off. Once this A.C. current reaches the voltage rectifier regulator it will be changed from A.C. to D.C. by the rectifier set up. If this is a half wave rectifier then for 1/2 the cycle time period the voltage will be a rising and falling and for 1/2 the cycle the voltage will be 0 as the negative parts of the current wave are blocked by the rectifier diode - keep in mind that this is all happening many times per second. If this is a full wave rectifier bridge then there will be four parts of the cycle that will have a current signal that will start off at 0 volts and rise to whatever voltage the regulator allows (13.8 to 14.2 volts) before it conducts anything higher to ground – usually through a zener diode set up. In either case there is still going to be a predominately D.C. signal (voltage is all flowing one way only) but since the voltage is constantly rising and falling from 0 volts to 13.8 – 14.2 and then back to 0 again it will also have what may be viewed as an A.C. component riding along that is now being radiated throughout the wiring coming from the voltage regulator rectifier to the ignition switch and the ignition coil. The frequency on this A.C. component will be determined by the engine speed and how many cycles per second the signal from the stator is plus any extra noise introduced by the zener diode turning on and off to shunt any excess voltage to ground.

This is very similar to the way a power supply in a home radio works where you have 110 volt A.C. coming out of the wall plug which is then transformed down to 12 volts by a transformer and then rectified with a diode bridge so that only D.C. current flows into a voltage regulator to control the voltage level in the radio circuit. However in radios they will have an electrolytic capacitor (probably around 3300 uF 50 volts) directly after the diode bridge to act as a storage device to filter out the voltage drops and rises reaching the radio circuit. I would imagine that if you looked into the construction of the regulator / rectifier there is probably no capacitor as very few tractors are equipped with a radio or any other device that would be adversely affected by a bit of A.C. component being passed into the D.C side of the system . As a result the tractor charging circuit relies on the 12 volt storage battery to act as a filter to absorb and maintain a reasonably stable voltage supply to the coil which it does but probably not as effectively as a dedicated capacitor placed directly at the coil might. Also there is probably a few feet of wire between the battery and the ignition coil which can become an excellent antenna to absorb and radiate any surrounding A.C. signal as well as become resonant at certain frequencies which can compound the problem resulting in R.F.I being generated that the antenna wire of the tach may be picking up and mistaking as a plug firing .

Hope this makes sense to you and others who read it. One other thing you could try would be to temporarily power the ignition coil circuit from another 12 volt storage battery that is not connected to the charging system on the engine. That may help determine if the tach antenna wire is picking up stray A.C. being introduced into the ignition coil via the charging circuit. If it is then you could try and connect the positive lead of a 3300 uF 50 volt electrolytic capacitor where the D.C. wire exits the rectifier regulator and the negative lead of the capacitor to a nearby ground - again keep all leads as short as possible. The capacitor may help to reduce any A.C. component from entering into the D.C. side of the charging circuit.

Interesting that you mention the problem with the digital VOM not giving a reading as I had the same problem years ago trying to check the voltage level in the charging system on my Bolens 1050 which used a starter generator. Had to use my dads old analog meter which worked fine. Since then I have purchased a more expensive digital meter and when I was building the electronic regulator for my Bolens 1053 I used it as well as an analog meter and both worked fine with it to read voltage with the engine running.
 
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