need some tutelage on how electric choke, 3-wire alternator, and coil interact, 470

natemoore

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In one of my other posts regarding my alternator not charging, someone mentioned that during cold starts, an extra amount of voltage is sent to the coil so the spark is nice and hot.

I'm not sure if my wiring is correctly installed (clipped and capped off wires) or if my electric choke is even working. I don't even know how the electric choke is supposed to work.

Firstly, there is 12V going to the choke when the ignition is on. Verified that with a voltmeter. Does this voltage heat up the coiled metal tape inside the choke housing and cause the choke to open up? Is it a bi-metallic strip? Wouldn't the heat coming off the engine cause the bi-metallic strip to do its thing and open the choke plate? Does the choke also control the "extra voltage" going to the coil during cold starts? Which side of the coil should it go to, (+) or (-)? The black wire coming from the alternator goes to the (+) terminal on the coil, as does a resistance wire. How should all this stuff work? Please tootle me or point me to a good discussion.

Specific questions: Is the battery sense (red) wire coming from my 3-wire alt the way the alternator measures battery voltage and thus regulates the output voltage, or is it how the battery excites the stator coils (since from my reading on the internet, the three wire isn't self-exciting)? Or does it do both?

An online retailer of my alternator labeled the black wire as "ignition switch wire +12V with engine running." Is this an input or output? I'm assuming an output since this is the wire that is hooked up to the (+) side of the coil.

Sorry for bombarding you all with questions, but I feel like I don't quite know enough to even ask the right questions.

Thanks.
 

boattoy

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

the wire from the coil to the alternator is prob your ignition switch(excite) wire. battery sense is just that... it senses voltage so the alternator charges at the correct voltage. so it can be connected to the output wire if you want. the coil wiring is a purple wire that goes to the choke then splits at the choke to another wire which is a resistance wire to drop the voltage for the points ignition. the choke doesnt control anything but itself. There is also a purple/yellow that goes from the ignition(usually labeled "I") post on the starter slave solenoid. when cranking is puts full voltage to the coil while cranking. If you have pertronix conversion you can get rid of the purple/yellow and the resistance wire from the choke to coil and just split off the wire going TO the choke. I just cut off the resistor wire at the choke. look up a repair manual for a wiring diagram and it will make sense. Its a very basic diagram.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

So, going back to a question that I asked in a different thread, if the black wire from the alternator to the (+) side of the coil broke off, the alternator would not charge because the stator coils aren't being excited? Someone else said it should still charge because the black wire going to the coil (+) was there to provide voltage to the coil windings. I'm a little confused.

http://forums.iboats.com/showthread.php?t=505530

I've had a Pertronix conversion kit in the garage for over a year and am finally ready to install it.

Thanks for the good info.
 

boattoy

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

if the excite wire to the alternator never gets 12 volts it will never charge no matter what. Only one wire alternators charge without anything else hooked up because they excite off of RPM.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Read some articles linked from ehow.com. Looks like the consensus is that the small red wire senses the battery voltage and the VR boosts/decreases alt output according to the load on the electrical system. Black wire is the excite wire. Tnx.
 
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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Here is a link to the factory wiring which I'm sure you have, but so we can reference. The original set up has two wires to the (+) side of the coil, each are powering the coil at different times. One from the elect. choke which is a purple resistance wire, and another wire from the starter solenoid which is a purple/yellow wire.

The starter solenoid gives the coil full 12v while you are cranking the engine over to start it. when you release the key, that wire (purp/yellow) is now dead and the coil is now getting "reduced power" thru the resistance wire (purp) from the choke.

The choke has 12v as long as the key is in "run" position, but the resistance wire reduces it to the coil.

The (+) terminal on the coil should not get any alternator wires to it because it is not full 12v while running.

You could grab 12v off the choke. You mention the Pextronix kit, that might change wiring to the coil, it might need full 12v all the time.

Not sure if I helped or made matters worse.:confused: :D
 

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

In one of my other posts regarding my alternator not charging, someone mentioned that during cold starts, an extra amount of voltage is sent to the coil so the spark is nice and hot.

I'm not sure if my wiring is correctly installed (clipped and capped off wires) or if my electric choke is even working. I don't even know how the electric choke is supposed to work.

Firstly, there is 12V going to the choke when the ignition is on. Verified that with a voltmeter. Does this voltage heat up the coiled metal tape inside the choke housing and cause the choke to open up? Is it a bi-metallic strip? Wouldn't the heat coming off the engine cause the bi-metallic strip to do its thing and open the choke plate? Does the choke also control the "extra voltage" going to the coil during cold starts? Which side of the coil should it go to, (+) or (-)? The black wire coming from the alternator goes to the (+) terminal on the coil, as does a resistance wire. How should all this stuff work? Please tootle me or point me to a good discussion.

Specific questions: Is the battery sense (red) wire coming from my 3-wire alt the way the alternator measures battery voltage and thus regulates the output voltage, or is it how the battery excites the stator coils (since from my reading on the internet, the three wire isn't self-exciting)? Or does it do both?

An online retailer of my alternator labeled the black wire as "ignition switch wire +12V with engine running." Is this an input or output? I'm assuming an output since this is the wire that is hooked up to the (+) side of the coil.Sorry for bombarding you all with questions, but I feel like I don't quite know enough to even ask the right questions.

Thanks.

The black "ignition wire" is input for the alt. and needs switched 12v to turn on the alternator. (The + side of the coil only gets full 12v during cranking the engine over)

The output of the alternator is the stud in the back of it, usually a large red wire will go from it to the battery. It will have power there all the time as it connected to the battery.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Okay. You guys have given some good explanations of the "extra voltage" to the coil. I also fully understand a three wire alternator. The last question to make it all complete is the one about the 12v at the choke causing the bi-metallic strip coil to heat up and open the choke. Is that how it works?
Thx.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

I've got that diagram. What I have on the (-) side of the coil is correct: gray wire going to tach and black ground wire coming from the distributor.

One the (+) side is the black excite wire going to the alternator, the resistance wire coming from the choke, and the purple/yellow wire coming from the slave solenoid. There is another looks like solid purple wire that has been cut and capped off. :confused:

Question comes to mind with this setup: Do I want full voltage going to the black excite wire to the alternator or will the reduced voltage coming through the resistance wire suffice?
 

boattoy

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

If you dont have points you want 12 volts to everything
 
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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

The alternator is going to want full 12v when the enging is running.
 

scv76

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Hmm, glad I ran into this post,.
I had a similar question not too long ago .....http://forums.iboats.com/showthread.php?t=487975

It makes total sense too me to have full battery volts going to the alternator, but it has never been clear to me which of the alternator wires it would connect too. Confusion is compounded further by the alt. kit installation instructions...see below

Looks like everybody here is in agreement that the Black wire from the alternator is the "excite" wire and should be connected to full battery voltage.
This is where it gets confusing..

Eric, you said "The (+) terminal on the coil should not get any alternator wires to it because it is not full 12v while running. "

natemoore said "On the (+) side is the black excite wire going to the alternator, the resistance wire coming from the choke, and the purple/yellow wire coming from the slave solenoid. There is another looks like solid purple wire that has been cut and capped off."

I purchased my alternator kit from Breezeworks, which is supposedly is a site that deals only with 470 products, and I would assume they would be familiar with how to wire their kit to our engines.

The installation instructions they provided clearly say in step #7 to connect the black wire with the terminal ring to the coil positive.
Then in step #16 they say to connect the other end of the black wire to the black wire from the alternator.

The red wire from the alt. and the output wire are connected together and go to the positive post of the starter solenoid.

So it would seem as if the installation instructions provided are incorrect, in that they have the black wire connected to a reduced voltage due to the resistance wire.
Do we need to notify Breezeworks of this potential problem?

The question now is, what effect does this have on the charging system?
Does the voltage regulator see the difference between the black wire, and the battery voltage on the red wire and always try to charge? This would cause an overcharge condition and ruin the battery.
My system as of now is wired with the black alt. wire going to the coil (+). I see over 14 volts at the battery with engine idle at about 700 rpms. This voltage seems in the ballpark since according to Breezeworks, the alt. is supposed to charge even at idle.
I have yet to change the black wire to full battery voltage and take a voltage measurement to see if there is any difference noted.
Interesting huh?
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Yep. It is interesting....and a little confusing. But I don't think the alt would be overcharging with the reduced voltage on the black excite wire. The red battery sense wire is the one that the VR uses to determine when to charge and at what rate.

As for my setup, when I get my alternator, I'm going to run 12 volts straight to the black excite wire and also to the Pertronix module....however as I type this I'm wondering how I can put 12 volts through the module but still use the resistance wire to the coil since I'm using a 1.5 ohm coil. Seems to me that the module is what sends current through the primary (low voltage) side of the coil, therefore, it must be installed in series with it. It seems pointless to install the resistance wire in between the module and coil, excuse the pun, but I guess that would be equivalent to having a 3 ohm coil, huh? The coil's instruction sheet said that I could omit the resistance wire if I were using it in racing applications. 45 mph tubing, anyone?

Shoot the dude at Breezeworks an email. Maybe he'll give us more insight, or maybe we'll enlighten him. :)
 

mannieg702

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Mar 10, 2011
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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

This is very interesting and what i needed to know as i just finish setting my 3wire set up last week. Now how hot should the alternator get? I'm just currious since this is the first boat i own and its been a learing proces. I did a top mount conversion, made my own brackets.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Pertronix Tech Rep Explanation

It's not acting like a short to ground. What you are seeing is the resister
wire at work in the ignition circuit. The points and Ignitor work in the
same exact way. They take the negative side of the coil on and off ground.
This is easy to explain but is going to be long winded. So here we go:

A resister only works (drops voltage) when it has current drawn
through the resister. So in less you have a something drawing current
through the resister (i.e. the Ignitor or points) you will read 12-volt at
the end of the resister (coil positive in this case). Current gets drawn
through the resister when ever the negative side of the coil goes to ground.
The negative side of the coil goes to ground every time the coil is being
charged up to make spark. Depending on the resistance in the resister and
the resistance of the primary of the coil, well determine how much voltage
you see on coil positive. So, depending on whether the Ignitor or points are
in the open (off ground) or closed (going to ground) it will determine what
type of voltage you see on coil positive.
In your case the Ignitor just happens to be lined up in the closed
position. So, when you connect the Ignitor red wire the circuit is completed
and goes to work. The same would happen if you hooked and unhooked the black
wire. Same should happen if you hooked the Ignitor red wire to battery
positive completely off the coil. In fact you can make the same thing
happens without the Ignitor. Disconnect all the Ignitor wires from the coil
and place a jumper wire from coil negative to ground. Turn your key on and
you will see the same voltage drop. That is because the current is being
pulled through the coil and dropping the voltage across the resister. This
is all normal and shouldn't be worried about.

When ever a resister is in the ignition circuit it must be bypassed with the
Ignitor red wire. Like our figure 3 wiring diagram. So, the Ignitor red wire
goes to the 12-volt side of the resister or in the case of a resister wire
to the location that this wire starts. In a mercurser that would be at the
choke. (See attached wiring diagram)

Now on the coil resistance. It just so happens on 4 cylinder application
the Ignitor and points have the same spec. So, that will make this easy. The
Ignitor and points can only handle 4 amps passing through them or they will
burn out. You can get the 4 amps in a two different ways. One is by using a
combination of resister and resistance in the coil; the other is by just
having the correct amount of resistance built into the coil. One way isn't
really better then the other in my opinion. Some opinions very on this fact.
To only get 4 amps across your ignition system that would require
3.0 ohms. You can figure that out by taking your battery voltage and
dividing your resistance to determine amps. (12V/3.0ohms=4amps). In your
case mercuser used a 1.5 ohm resister wire and a 1.5 ohm coil adding up to
the 3.0 ohms. So, removing the resister and running 12-volt to the 1.5 ohm
coil will cause the ignition (Ignitor or points) to handle 8 amps. Double of
what it can and it will burn out. Race applications are different because of
RPM range and amount of time spent in the charge cycle. Trust me you would
never use it in a 4 cylinder boat application.

I hope this answers your question. In short you should be placing the
Ignitor red wire on the incoming side of the resister wire at the choke. And
you can't remove the resister in less you change the coil to a 3.0 ohm coil
or you will burn out your ignition.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Don, maybe the post title should include "distributor" or "points/electronic ignition" since it's turning into a Pertronix thread. :)
 

Don S

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Here is how the wiring SHOULD be done on that particular alternator.
I did it in .pdf format so you can enlarge it and see it better.
 

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natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Here is how the wiring SHOULD be done on that particular alternator.
I did it in .pdf format so you can enlarge it and see it better.

Thanks Don. Looks like the battery sense is sampling up near the ignition switch further away, according to page 4E-6. Breezeworks wire diagram had it going to starter solenoid, the same terminal as the battery cable. This seems to make more sense (damned, another unintentional pun!).

I just happen to have a purple wire close by. It used to be connected to (+) coil on the same crimp-on terminal as the purple/yellow wire, but someone cut and capped it off. It looks like a factory original crimp, too. Wonder why they had it set up like that? Did these things ever come with a 3 ohm coil and no resistance wire?
 

Don S

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

Looks like the battery sense is sampling up near the ignition switch further away, according to page 4E-6.

I don't think you understand the purple wire on your engine comes from the purple wire on your ignition switch. (One other thing you might not have noticed on page 4E-6 is the ignition switch letters on the switch are backwards for the I and B terminals. So keep that in mind.). Best to go by wire colors on the ignition switch, not the letters on the switch.

The purple wire should come all the way from the helm to the engine. The alternator is not "Sampling" from the switch, the purple wire on the switch better have the same exact voltage as the purple wire on the engine. If it doesn't then you have something wrong somewhere.

Your wiring should be like shown on the wiring diagram, that is how Merc sent them out from the factory. WITH the resistor wire.
 

natemoore

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Re: need some tutelage on how electric choke, 3-wire alternator, and coil interact, 4

I don't think you understand the purple wire on your engine comes from the purple wire on your ignition switch. (One other thing you might not have noticed on page 4E-6 is the ignition switch letters on the switch are backwards for the I and B terminals. So keep that in mind.). Best to go by wire colors on the ignition switch, not the letters on the switch.

The purple wire should come all the way from the helm to the engine. The alternator is not "Sampling" from the switch, the purple wire on the switch better have the same exact voltage as the purple wire on the engine. If it doesn't then you have something wrong somewhere.

Your wiring should be like shown on the wiring diagram, that is how Merc sent them out from the factory. WITH the resistor wire.

Hmmmmm. Not getting why you think I'm confused about the purple wire with regards to hooking it up to the black excite wire. That's what your diagram shows and that's what I'm planning to do, complete with resistance wire. I was just curious why it was originally wired with purple to coil (+). BTW, the purple does provide a switched 12 volts, right? Are you implying that purple is unswitched 12 volts? If so, then there's my confusion and your clarification. I'll go measure with ignition switch on and off to be sure.

As far as "sampling", I remember reading in one of those many alternator articles that the battery sense should be hooked up to the wiring harness as far away from the battery and alternator as possible because when you start turning on power consuming accessories, the alternator VR will get a better reading. Maybe it's a moot point for a boat since we're not running air conditioners and headlights on high beam.

Your second paragraph: did you mean to say Red/Purple instead of purple since you're talking about battery sense?

Regardless, I think I have it all figured out now. Thanks!
 
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