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Tractor Talk Discussion Forum

12V Conversion

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RL

03-13-2004 18:12:00




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Just like opinion about using 12V vs 6V components. My tractor has been coverted from 6V generator to 12V alternator. The questions is do I use resister in line with original 6V coil, condenser and points? Or, eliminate the resister and use a 12V coil and replace the condensor and points. I.e, 12v all the way through. Thanks




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RL

03-14-2004 15:54:42




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 Re: 12V Conversion in reply to RL, 03-13-2004 18:12:00  
Thanks y'all,
I guess the bottom line is discuss it with the parts man, oops! person and just make the decision. I'm kinda leaning towards a 12V coil with a built in resister. That way it will look more original than an after market resister hanging off somewhere.



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Tom in TN

03-13-2004 21:21:34




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 Re: 12V Conversion in reply to RL, 03-13-2004 18:12:00  
RL,

Many guys on this forum know more about this than I do, but here's my two cents worth. The points and condensor don't matter, however, all of the other electrical components on your tractor will be effected by this change. All of your lights (headlights, taillights, dash lights) will burn out pretty quickly if you don't change them to 12 bulbs. Your gas gauge and temperature gauge may not register properly with the higher currents that will be created in their circuits as a result of increasing the voltage drop across them.
If you have a mechanical tachometer that formerly was connected to the back of the 6 volt generator, you won't have any way to reconnect it to your new alternator. Your starter motor will now run faster than it previously did. That's probably not a bad thing, but if you have trouble starting your engine, and run the starter for any extended period of time trying to get the engine started, the starter motor will generate much more heat than it previously did when you only had six volts being applied to it.

Although many guys think the conversion is good, personally, I don't think the conversion is worth it. I think that you would be much better off leaving the six volt system in place and simply keeping your generator/battery in good condition.

I'll probably get flamed for expressing this opinion, but there you have it.

Good luck,

Tom in TN

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old

03-13-2004 20:13:36




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 Re: 12V Conversion in reply to RL, 03-13-2004 18:12:00  
Just ask for a 1969 chev coil pickup that is and it will work just fine



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B

03-13-2004 19:13:43




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 Re: 12V Conversion in reply to RL, 03-13-2004 18:12:00  
When I converted mine, I bought a brand new coil 12V WITH INTERNAL RESISTOR. I just had to mke sure the total resistance was around 3.3 ohms.



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RL

03-13-2004 19:51:56




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 Re: Re: 12V Conversion in reply to B, 03-13-2004 19:13:43  
B,
Is this a standard 12V coil or something special? When purchasing, did you have to specify 3.3 ohms resistance and by any chance do you have a part number? Also, is there a need to replace the points and condenser with something other than the originals for use with the old 6V system. Thanks



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B

03-14-2004 08:32:52




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 Re: Re: Re: 12V Conversion in reply to RL, 03-13-2004 19:51:56  
I simply ask for a 12V coil with an internal resistor.

At the time I did the change over to 12 volts, I was not only changing for a 12 Volts alternator but also replacing the ''points and condender'' by a magnetic pickup device made to fit my distributor. I wanted to keep the wiring as simple as possible so I didnt want a resistor exposed next to my coil. What type of tractor/distributor do you have?

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RAB

03-13-2004 23:55:31




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 Re: Re: Re: 12V Conversion in reply to RL, 03-13-2004 19:51:56  
RL,
A coil is a coil, but not all coils are the same. Confused?
The rate of current rise is important as the coil 'turns' oppose this increase. It's called inductance. The current through an inductor rises exponentially with time - faster at first, then more slowly
Supposed 'sports coils' have a lower resistance and inductance, allowing more current and therefore more spark energy, but points have to handle this and burn up faster than standard coils. They are only better at high revs.
A 12 coil is 12 volt unit or a lower voltage unit with a resistor in series to reduce the maximum current to a safe value. The resistance will limit the non-running current through the coil (if the points are closed when the engine stops).
A ballast resistor coil is a lower voltage coil (6 or 8 volt) with an external resistor in circuit at all times, except on cranking with starter motor. This allows more current to flow for a stronger spark energy at cranking voltage.
Points and condenser operate at 12 volts while closed and open, but have to cope with about 300 volts when the points are just opening due to the inductive voltage generated by the coil as the current in the coil is turned off (and the magnetic field collapses). No change for either voltage, generally. Old ones for 6 volt systems were probably better than those for newer 12 volt systems as they had to pass more current for equivalent spark energy!
One of the most important factors of the Ketteringham circuit is probably the dwell angle - the time the points are closed, allowing the current to build up in the coil, but for a 4 cylinder tractor running at 1500rpm it is less important than, say, an 8 pot motor running at 5500rpm as the theoretical spark enegy is proportional to the current flowing at the time the points are opened (provided no energy is lost back across the points as they open, etc etc.)
Things are a mite more complex than above, but I think I have given you enough to think about!
There are some super internet sites which explain the Ketteringham system better than me.
Regards,RAB
Regards, RAB

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RL

03-14-2004 07:16:08




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 Re: Re: Re: Re: 12V Conversion in reply to RAB, 03-13-2004 23:55:31  
RAB, you've done just fine. I'd give you an 'A' on your thesis. How does one with your impressive knowledge feel about using the 6V vs 12V coil in a 12V system, should I use a resistor with either, and is there any concern about what type of condenser I use? Thanks



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john

03-14-2004 14:58:00




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 Re: Re: Re: Re: Re: 12V Conversion in reply to RL, 03-14-2004 07:16:08  
I would have to give RAB a C- on his thesis. He has a very good page of amps volts laws ect but you are still asking your original question.

Using a 6 volt coil points and condenser in a 12 volt system is ok as long as you use a 12 to 6 volt resistor. What is the part #? I do not know ask the parts man for a 12 to 6 volt resistor. Do you need another resistor inline with this one? I do not know. Some do some don't. Did you have one before? If so use it.

Using a 12 volt coil with your original 6 volt condenser is possible. The condenser is often over built and can take it. Does your 12 volt coil need a resistor? This is a deep dark secret that only your parts man knows as we do not know your tractor brand or which 12 volt coil you picked out. Some 12 volt coils require a resistor and some do not. Some use one resistor but another will use a totally different resistor.

As to one over the other that is up to you. I like to use the 12 volt coil myself but I like electronic ignition also and that is more expense. The 6 volt system will work with the proper resistor.

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Larry from MD

03-14-2004 15:20:12




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 Re: Re: Re: Re: Re: Re: 12V Conversion in reply to john, 03-14-2004 14:58:00  
I can add a little to this GM cars and trucks had a resistor built into the wireing,so if you get a gm coil you do need a resistor.I have the napa numbers but they are way more expencive than farm sources.



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