Electrical power seems low...

[JimF]

I re-wired my newest narrowcase 250, the so-called 'magneto' version where the whole electrical system runs on AC voltage.

The alternator has two coils. I used one coil solely for the ignition system and the other for the lighting.

The bike started and idled fine, but the lighting system is confusing me.

With only the taillight on the voltage reading at idle is about 12 volts AC.

Once I turn on the headlight the voltage drops to under 3 volts. At that extremely low voltage the taillight and brake light no longer light as the voltage is too low to power the filaments.

So my thinking is as follows but I welcome other opinions or tests I haven't thought to do:

1) Perhaps one alternator coil is more powerful than the other and I put the powerful coil on the ignition (relatively lower power required) and the less pwerful coil on the lighting circuit which is why when I put a heavy load on the winding the voltage drops. Does anyone know if the coils vary?

2) My coils are weak for some reason - maybe the permanent magnet is weak? Or the coils are internally shorted?

Any recommendations?

[DewCatTea-Bob]

" I re-wired my newest narrowcase 250, the so-called 'magneto' version where the whole electrical system runs on AC voltage. "

____ Which version ? _ There were three different AC-type/AC-powered electrical-systems employed on n-c.250-models !
Does this "newest" 250 have the very-same system-type as a Mark-3 ? _ (For now, I'll assume so.)


" The alternator has two coils. I used one coil solely for the ignition system and the other for the lighting. "

____ Well it seems that you haven't paid too much attention to past threads on this topic, Jim.
Which alt.power-coil went to which load-circuit ? ...
The alt.coil with the yellow wire-lead is used for the ign.circuit & the brake-light circuit along-with the white wire-lead. _ While the alt.coil with just the red wire-lead is for the head & tail lights.


" Once I turn on the headlight the voltage drops to under 3 volts. At that extremely low voltage the taillight and brake light no longer light as the voltage is too low to power the filaments. "

____ Yep, as many others with such power-systems have long realized that that's been a well-known issue with the battery-less/AC-powered models ! ... Next to no lighting at idle,
(although there ought be at least a faint glow).


" 1) Perhaps one alternator coil is more powerful than the other and I put the powerful coil on the ignition (relatively lower power required) and the less pwerful coil on the lighting circuit
Does anyone know if the coils vary? "

____ Of course the two separate alt.coils are not exactly the same (for the AC-type system) ! ...
The alt.coil intended for lighting is wired for higher current (& lower voltage), while the other coil is intended for more voltage (& less current),, so it ought be somewhat obvious that the alt.power-coil meant for running the lighting-system, has a slightly heavier gauge of windings.
Since it seems that you didn't get the headlight to even glow, it's likely you've gotten the alt.power-coils mixed-up (from their intended jobs).
__ The lighting power-coil is capable of running either the INTENDED lighting-system or the ign.system, but the ignition alt.power-coil can't pass as much current to equally power-up the headlight.
Also, I've come-across a fairly large number of the "40 watt" alt.stators, where apparently others have used the lighting-coil to run the ign.system,, which since the ign.circuit is most-often shorted-out, the wrongly-connected lighting alt.power-coil had thus become darkened (if not outwardly burned-up somewhat).


" 2) My coils are weak for some reason "

____ That's doubtful (as a whole), but perhaps a single coil-loop has been sheered-down (to become as a bottle-neck & pinching-off current-flow).


" maybe the permanent magnet is weak? "

____Perhaps a possibility.


" Or the coils are internally shorted? "

____ If so, then you'd not be able to get ANY voltage-reading to speak-of.


" Any recommendations? "

____ Well first, the wiring should be redone CORRECTLY.
Just how do you currently have it wired-up exactly ?


Hopeful-Cheers,
-Bob

[JimF]

Well, let me say from the onset that I eliminated the part of the original wiring that used the brake light filament to ground the ignition circuit.

Keep in mind that the original wire's insulation was crumbling to the touch and I had used a AC line cord to replace the three wire 'pigtail' leading from the coils out of the engine case. For this reason all reference to wire colors has no validity anymore.

So as to simply explain this rather simple circuit I have two coils and each coil has a wire end at each side. One end of one coil is internally grounded and so only three wires come out of the engine case as it was from the factory.

Regarding the pair of coil wires leaving the engine case that are opposite ends of the same coil I grounded one of the two wires.

That leaves me with two wires presenting AC voltage swings when referenced to the frame.

I used one of the two wires to power the lighting circuit (headlight, tail and brake light) and the other wire to power the ignition circuit (HV ignition coil.)

I failed to notice when I took the alternator coil assembly out that the wire gauge was different between the two coils mounted on the plate. In retrospect that is something I should have looked for.

Also I should have made a quick notation of the old wire insulation colors and which new color in the AC line cord was being used. I was in a great rush that evening as I had some help to take out and replace the alternator but time was critical.

Getting back to the present, as I have spade terminals on the three wires leaving the engine case I could within minutes swap the two coils so that they switch functions; that is to say I can quickly flip the two coils between the lighting circuit and the ignition circuit.

Seemingly that is my next move.

Jim

[DewCatTea-Bob]

" I eliminated the part of the original wiring that used the brake light filament to ground the ignition circuit. "

____ Well that MAY be okay if you didn't care to have a usable brake-light for legal street-riding (during darkness / with headlight turned-on).
It seems that you have now got your project wired-up somewhat the same as the original 250 Motocross & Mark-III models (which had no brake-light circuit !).

" Keep in mind that the original wire's insulation was crumbling to the touch and I had used a AC line cord to replace the three wire 'pigtail' leading from the coils out of the engine case. For this reason all reference to wire colors has no validity anymore. "

____ This idea of using a AC/(PC) line-cord to replace the original alt.cable was covered previously within another past thread,, and I then logically advised that it's green-wire ought be used for the ground-circuit connection, and it's white-wire (most logically) for the lighting-circuit.
So if any such logic was followed when the chosen replacement-cable was installed, then the new colors should still have at least a little "validity".


" I have two coils and each coil has a wire end at each side. One end of one coil is internally grounded and so only three wires come out of the engine case as it was from the factory. "

____ Okay-then, I (hopefully) assume that the alt.power-coil which was the one that ended-up with a PAIR of wires connected (to just it alone), turned-out to be the very-same power-coil which Ducati had the original yellow & white wires connected to !?
If this obvious logic (which you seemed to have cared to follow) was not kept well noted of, then some ohm-meter testing ought to be done to check-out what's really what, as you now have it.


" Regarding the pair of coil wires leaving the engine case that are opposite ends of the same coil I grounded one of the two wires. "

____ That's of-course to be expected, and hopefully that was the green-wire (& connected to the ign.power-coil), and thus leaving the black-wire (from the ign.power-coil) for leading to the other-end of the ign.circuit.


" That leaves me with two wires presenting AC voltage swings when referenced to the frame. "

____ Right, one wire-lead for the ign.circuit and the 2nd.one for the lighting-circuit, (unfortunately both currently of unknown color).


" I used one of the two wires to power the lighting circuit (headlight, tail and brake light) and the other wire to power the ignition circuit (HV ignition coil.) "

____ Well (as I indicated previously), either alt.output will be able to power-up the ign.circuit (with/without the brake-light circuit included), HOWEVER, while the alt.power-coil that was originally intended to power the tail & headlight circuits only, can indeed power-up a brake-light,, it cannot possibly provide enough power-juice to (fully) run the headlight AND also the brake-light at the same time ! _ At best, you might be able get both those lights to produce a notable 'glow' near top-RPM, (off-from the lighting power-coil).
So with YOUR wiring-system wired-up as you've indicated, sometime when you're in actual need of your headlight-beam and see reason to brake your speed, then be prepared to not only loose your headlight's projected beam intensity, but also realize that YOUR brake-light will not brighten-up your taillight (as is normally expected), either !


" I failed to notice when I took the alternator coil assembly out that the wire gauge was different between the two coils mounted on the plate. In retrospect that is something I should have looked for. "

____ Sure should've, cuz it's been covered within a number of past threads, that the two different alt.power-coils have different resistance-readings, (with the lighting-coil having the lowest ohm-reading).


" Also I should have made a quick notation of the old wire insulation colors and which new color in the AC line cord was being used. I was in a great rush that evening as I had some help to take out and replace the alternator but time was critical. "

____ Well that's too bad, cuz that oversight has next lead to your current troubles now.
I've always hated having any such "help" around during my-own project-work, cuz the company always tends to make me forget about some detail or another.


" as I have spade terminals on the three wires leaving the engine case I could within minutes swap the two coils so that they switch functions; that is to say I can quickly flip the two coils between the lighting circuit and the ignition circuit. "

____ Right,, and hopefully that will solve your (extra) dim headlight, (so long as you also got your 'PAIR' of wire-leads connected to the particular alt.power-coil which was intended for the ign.circuit).

____ As for a usable brake-light (regardless if the headlight is turned-on), you will need to either rewire the system back like stock, or better yet, install a battery set-up to power the brake-light (& a horn).


Hopeful-Cheers,
-Bob

[JimF]

Thanks Bob,

But consider this....

____ Well that MAY be okay if you didn't care to have a brake-light for street-riding.
It seems that you have now got your project wired-up same as the original 250 Motocross & Mark-III models (which had no brake-light circuit !).

That's not the case, I have a brake light circuit that works. Power for the brake lamp filament is wired through the brake switch (single pole, single throw, momentary contact normally open) to the same potential as the headlight and taillight. Step on the brake pedal and the switch closes sending power to the brake lamp filament.

All I've done is eliminate the crazy method of grounding the ignition coil through the brake switch and brake light filament.

____ This idea of using a AC/(PC) line-cord to replace the original alt.cable was covered previously within another past thread,, and I then logically advised that it's green-wire be used for the ground-circuit connection, and it's white-wire (most logically) for the lighting-circuit.
So if any such logic was followed when the chosen replacement-cable was installed, then the new colors should still have (at least) SOME "validity".

Well, the line cord I found in my box of old computer discards was found to contain a green wire, a blue wire and a brown wire after the black outer jacket was peeled back. So not all line cords have white, green and black sheathed internal conductors. I chose this line cord as it utilizes a heavier gauge of internal wiring than any of the other line cords I had.

I did tie the green wire to ground effectively grounding one end of the coil it is connected to. I will swap the blue and the brown wires tonight to see if the lighting circuit has any more power when run off the other end of the coil.

I can check tonight to see which circuit (lighting or ignition) is now being run off the internally grounded coil and which circuit is being run off the externally grounded coil.

I am hoping the swap gives me more power. I understand that I am at low electrical power at idle, but I am by law required to have the headlight on. With the headlight pulling the voltage below the level needed to light the tail and brake filaments it currently means (excuse the pun) that even though the circuits are wired and working I have no function light of any kind (tail or brake) when at a stop.

If I turn the headlight off the voltage level rises and the brake an tail work fine, but I have no headlight which is, in my State of residence, illegal.

Jim

[DewCatTea-Bob]

" But consider this....
That's not the case, I have a brake light circuit that works. Power for the brake lamp filament is wired through the brake switch (single pole, single throw, momentary contact normally open) to the same potential as the headlight and taillight. Step on the brake pedal and the switch closes sending power to the brake lamp filament.
All I've done is eliminate the crazy method of grounding the ignition coil through the brake switch and brake light filament. "

____ Apparently Jim, you have not yet read my ENTIRE (previous) post !
Please try again, (so as to realize why it really can't be expected that the single power-coil could possibly power the lights AND the brake-light, TOGETHER AT THE SAME TIME).
__ That "crazy method" was the convenient way to make use of the excess power that's otherwise simply shorted directly to ground (whenever the ign.points are closed) ! _ As the lighting power-coil is already taped-out to it's max.output (whenever running the lights) !


" Well, the line cord I found in my box of old computer discards was found to contain a green wire, a blue wire and a brown wire after the black outer jacket was peeled back. So not all line cords have white, green and black sheathed internal conductors. "

____ Well in that case, (other than Ducati having used the color 'green' to reference ground-conductors), I guess there was no obvious logic to apply to those two other odd colors that you ended-up with.
(However if we consider what those odd colors would look like in a black & white photo, THEN the blue-wire would look LIGHTer [than the brown], and-so ought be the choice for the output to lights.)


" I did tie the green wire to ground effectively grounding one end of the coil it is connected to. "

____ I wonder which alt.power-coil it was (randomly?) actually connected to ?


" I will swap the blue and the brown wires tonight to see if the lighting circuit has any more power when run off the other end of the coil.
I am hoping the swap gives me more power. "

____ I wouldn't expect a 'night & day' difference when you try-out that flip-difference.


" I can check tonight to see which circuit (lighting or ignition) is now being run off the internally grounded coil and which circuit is being run off the externally grounded coil. "

____ Right but still, it also ought be realized & straightened-out as to which wire-colors you actually have connected to whichever power-coil type.


" I understand that I am at low electrical power at idle, but I am by law required to have the headlight on. With the headlight pulling the voltage below the level needed to light the tail and brake filaments it currently means (excuse the pun) that even though the circuits are wired and working I have no function light of any kind (tail or brake) when at a stop.
If I turn the headlight off the voltage level rises and the brake an tail work fine, but I have no headlight which is, in my State of residence, illegal. "

____ Now you too have come to personally understand the plights of those of us who have had to put-up with the somewhat insufficient stock AC-powered only electrical-systems.
__ I most always suggested making use of the significant alt.power that's otherwise completely wasted by the ign.circuit, to instead charge a battery (rather than merely power the brake-light, as stock).


Dukaddy-DUKEs,
-Bob

[JimF]

But just to make sure I understand you....


Regardless of color (since my colors are off) the coil that presents its two ends on the pigtail from the engine is used for the ignition circuit, while the coil that presents only one end on the pigtail (while the other end is internally grounded) is the lighting coil - is that correct?

AND you are telling me that there is a difference between the two coils, and that the coil we are calling the lighting coil is somewhat wound and constructed to provide for the high current needs of the headlight?


Jim

[DewCatTea-Bob]

" the coil that presents its two ends on the pigtail from the engine is used for the ignition circuit, while the coil that presents only one end on the pigtail (while the other end is internally grounded) is the lighting coil - is that correct? "

____ If we've indeed been in reference to the '40 watt' alt.version, then YES, (as can be confirmed by the common workshop-manuals). ...
The alt.power-coil that's meant to power the ign.circuit has/had a yellow-wire (connected to it at one end), to go directly to the ign.coil-circuit,, while the opposite-end (of that same alt.power-coil) has a white-wire connected it, to either go directly to ground OR through the brake-light's filament & onward to ground (depending on whichever state the brake-light switch is at).
And the other alt.power-coil's output (which is/was available through a red-wire), is intended to power (only) the tail & headlights (which are of-course both grounded so as to complete their circuits back to that internally-grounded alt.power-coil).
__ Worthy of note, is that the expected headlight-bulb (for this AC-system), is to be just 18 to 25 watts.


" AND you are telling me that there is a difference between the two coils, and that the coil we are calling the lighting coil is somewhat wound and constructed to provide for the high current needs of the headlight? "

____ For the alt.stator that's believed you seem to have, then YES. ...
While I don't recall the difference in wire-gauge or winding-loops (between the two different power-coils), I believe that the one intended for the lights has a slightly thicker gauge and fewer winding-loops (than the alt.power-coil intended for the ign.system).
This difference can be backed-up by using an ohm-meter to see that the power-coil intended for the lighting has a lower ohm-reading.
__ With the old 4-pole Monza-type alt.stator, both it's power-coils are the same (as you seemed to have assumed),, however the particular power-coil that was produced to specifically power the AC-type ignition set-up, which spends most of the produced power-juice directly shorted back to itself (though the ground-connection), would get overheated if it could possibly pass (directly to ground) as much current-juice as the power-coil that's meant to run the lights would, (when presented with such a short-circuit as the ign.circuit includes).
Also, I believe the ign.power-coil is also meant to create a somewhat higher voltage (than the lighting power-coil does), for helping to create a better spark (with the intended green-lable ign.coil).


Dukaddy-DUKEs,
-Bob

[JimF]

Well, I had the two coils reversed and so I flipped them the other way.

Did I see a difference?

Not really.

With the headlight on I go from glow at idle to a decent beam at good engine RPMs. This I could live with.

But, when one comes to stop the engine is usually at idle. The headlight on saps all the power and the taillight and brake light are undetectable.

I will mostly be doing daytime driving, so I merely want to give the local gendarmes as well as oncoming drivers the appearance that I am running with a headlight on while conserving the power to run the brake and taillight.

I have developed a triple Luxeon Rebel Star "light bulb" that runs at 6-volts DC. I fitted one with white LEDs and it knocks your eyeballs out. It consumes 1/2 of an amp (at 6-volts that's just 3 watts of power.) I am going to adapt this to the headlight. This is not legal (not DOT approved, no high/lo beam, etc.) and I don't recommend that anyone do this ever. In fact, I am telling you absolutely not to do what I am doing under any circumstances.

I once tried to use a commercial Luxeon ring to do this task, but this new 'bulb' is something different. This will look much more like I am running a regular bulb.

Being as the LEDs are DC animals I will need to rectify the AC voltage going to the headlight but I can do that with a $2.00 part from Radio Shack.

I'll probably document this conversion in another thread.

Jim

[DewCatTea-Bob]

" Did I see a difference?
Not really.
The headlight on saps all the power and the taillight and brake light are undetectable. "

____ So it seems that YOUR dim-lighting issue is not merely due to the slight difference in power-delivery between the two power-coils, but rather due to you trying to power not only the tail & head lights, but ALSO the brake-light as well,, all at once just with only the power of a single power-coil ?
If so, you should've first asked if that wiring set-up could work before wiring-up your system that way. _ As I had already tried that same set-up idea way-back when I was a teenager, and I then found that all three lights could barely be seen glowing !
But I did get a much better brake-light (than stock), so long as the lights were left turned-off.


" I have developed a triple Luxeon Rebel Star "light bulb" that runs at 6-volts DC. I fitted one with white LEDs and it knocks your eyeballs out. It consumes 1/2 of an amp (at 6-volts that's just 3 watts of power.) I am going to adapt this to the headlight.
Being as the LEDs are DC animals I will need to rectify the AC voltage going to the headlight but I can do that with a $2.00 part from Radio Shack. "

____ Is your plan to also INCLUDE the LED-lighting along-with an old/std.filament-type load as well ? _ Cuz if not, the alt.supplied (variable) available power will most certainly over-power 6v.LEDs (without some additional load to bleed-off excess power) !
So you'll likely need more than just a 2-buck rectifier, (like perhaps a low-duty v.regulator). _ Or consider a 12v.LED set-up, so as to increase longevity.


Hopeful-Cheers,
-Bob