6V tractor with 12V coil

[DanB53]

I just bought a McCormick-Deereing W4 that has 6v generator, wiring, voltage regulator and battery but a 12v coil. I haven't got it running it yet but before I do should I change coil to a 6v or does it matter?

 

[MIKE R]

Why don't you put a resistor in there. I think that's how Larrys Wd Allis was hooked up. A resistor like the one on my hit and miss engine is what he used. Running with the 12 volt coil will probably have to much resistance and make the engine have a weak spark.

 

[DanB53]

Thanks Mike I think I'll just buy a 6v coil and make it right.

 

[BobRip]

A resistor would make the spark weaker. On 12 volts you need a resistor with a 12 volt coil. On 6 volts I dont think (not absolutely sure) you do. I think I would run it. It might be hard to start when cold. On 12 volts systems they used to bypass the resistor on starting.

 

[heviduty]

Why don't you put a resistor in there. I think that's how Larrys Wd Allis was hooked up. A resistor like the one on my hit and miss engine is what he used. Running with the 12 volt coil will probably have to much resistance and make the engine have a weak spark.

Adding resistance would be counter intuitive. 12V coils actually run on about 6 volts so you are about right. The ballast resistor / resistor wire in series with the coil reduces the voltage. When starting, the battery voltage is low due to the heavy current draw, so the ballast / resistor wire is bypassed during starting to supply the coil with the full battery voltage. If it starts ok, don't worry about it. If the spark is weak and there is a ballast or resistor wire, replacing it with a piece of wire will help.

 

[Soundguy]

Adding resistance would be counter intuitive. 12V coils actually run on about 6 volts so you are about right. The ballast resistor / resistor wire in series with the coil reduces the voltage. When starting, the battery voltage is low due to the heavy current draw, so the ballast / resistor wire is bypassed during starting to supply the coil with the full battery voltage. If it starts ok, don't worry about it. If the spark is weak and there is a ballast or resistor wire, replacing it with a piece of wire will help.

man what an electrical mess this thread is.. but it's partly to blam on manufacturers labeling 6v coils as 12v, then in small print saying to use a resistor.

there are native 6v coils and native 12v coils.

a napa IC 7 is a native 6v oil.. runs on 6v, no resistor..

a napa ic14sb is a native 12v coil.. runs on 12v with no resistor.

putting a 12v coil on a 6c tractor is asking for problems and weak spark.

putting a 6v coil on a 12v tractor just means you need a resistor inline. many use a resistor or resistor wire and an ignition bypass setup or thermal coeficient ballast resistor to accomplish easy starts.

put a 6v coil on that 6v tractor.

TSC even has 6v coils.. probably cheaper than that napa ic7

 

[MIKE R]

Here is a picture of the distributor set up on Dan's tractor. Might help clear up any further confusion.

View attachment 280628

 

[Soundguy]

what are we suposed to be seeing.. it's a pretty common site to see a ign coil seting like that near a dizzy... nothing too special about it???

 

[MIKE R]

what are we suposed to be seeing.. it's a pretty common site to see a ign coil seting like that near a dizzy... nothing too special about it???

You weren't supposed to see anything unusual. I just felt like posting a photo of it.

 

[Soundguy]

oh, ok. nice photo then. paint looks great.

as much as I love ford red and grey and blue.. I also love the IH reds, case orange ( flambeau ), and the persion orange allis's

looking at a wd on the side of the road longingly right now.. it's calling to me...

 

[MIKE R]

oh, ok. nice photo then. paint looks great.

as much as I love ford red and grey and blue.. I also love the IH reds, case orange ( flambeau ), and the persion orange allis's

looking at a wd on the side of the road longingly right now.. it's calling to me...

The WD would go good with your G.

Now lets get back on the main topic of this thread it is getting off topic pretty quickly. 6V tractor with 12V coil

 

[DanB53]

Thanks for the input guys. I think I'll just leave it for now and see how it runs.

 

[Jerry/MT]

If you have a 6V system, you need a coil with 1.6 ohms reistance in the coil primary. This is usually called a 6V coil. A true 12 V coil will have a reisitance of 3.2 ohms in the primary part of the coil. This is to limit the primary current to a maximum of ~4 amps with 12v applied to the circuit.The are some so called "12V coils" that have a note printed on them "Use with a resistor". This is also a 1.6 ohm primary resistance coil.

Since you say you have a 6v electrical system, you'll need a coil with a 1.6 ohm primary resistance which will limit the primary current to ~4amps max.. A real 12 V coil on a 6v system will halve the primary current and make a weak spark.

 

[pat32rf]

The prior owner might have fried the 6 v coil, stuck in a 12v and found that it would start and run so left it with no ballast resistor. If he puts a 6v coil back in, then it will probably fry with no resistor.

 

[Soundguy]

why would a 6v coil fry on 6v? ford's about the only one innovative enough to do that trick. ie.. put a 4v coil in a 6v machine.. and a resistor that heats up when running.. thus giving you a cold start bump...