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12 volt coil voltage

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Clay

07-29-2002 22:01:45




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Anyone know what the voltage is supposed to be at the coil for a 12 volt system?I was told that my 8N that is still 6 volt should be 4.5 volts or less.Should the one that is 12 volt be around 8 volts??




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Dell (WA)

07-29-2002 23:22:15




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 Re: 12 volt coil voltage in reply to Clay, 07-29-2002 22:01:45  
Clay..... ....yes, I know what the voltages should be.

For a OEM 6 volt frontmount in a 6 volt system, you should read about 3.5 volt at the coil terminal. (2.5 min, 4.0 max) with the points closed. With the points open, you should read the 6 volt battery. Anything other volts is going to give you sparkie problems. You also have to use the infamous ballast resistor on the backside of your dash panel.

In a 12 volt conversion, IF you continue to use the OEM 6 VOLT frontmount coil, you should read about 3.5 volts (2.5 min, 4.0 max) with the points closed and 12 volt battery volts with the points open. You also have to use a 12 to 6 volt dropping resistor AND the infamous ballast resistor on the backside of your dash panel.

If you use the new 12 volt frontmount coil (my recommendation) you should read about 11 volts at the ignition coil terminal and DO NOT USE the infamous ballast resistor. USE INSTEAD a 0.5 ohm, 10 watt resistor from Radio Shack. UNDERSTAND?

Its the LAWS of Electronics..... .....Dell

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Greg

07-30-2002 06:44:13




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 Re: Re: 12 volt coil voltage in reply to Dell (WA), 07-29-2002 23:22:15  
Question Dell,
I have a front mount 8N that was converted to 12 volt, with the voltage dropping resistor and the ballast resistor and the 6 volt coil. With points closed I read 4.8 volts at the coil. This seems a little high. Which resistor is suspect?



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Dell (WA)

07-30-2002 17:20:25




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 Re: Re: Re: 12 volt coil voltage in reply to Greg, 07-30-2002 06:44:13  
Greg..... .....it would most likely be your 12 to 6 volt converting resistor is converting to 7 volts. If'n you're not having coil or point problems, leave it. Be greatfull..... ....Dell



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Salmoneye

07-30-2002 07:04:27




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 Re: Re: Re: 12 volt coil voltage in reply to Greg, 07-30-2002 06:44:13  
Is that on a 'hot' or 'cold' reading.

The longer the tractor runs the lower the reading from the 'ballast' resistor will be.
Or at least that is how I understand it.

Course...I drink...



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Greg

07-30-2002 10:13:20




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 Re: Re: Re: Re: 12 volt coil voltage in reply to Salmoneye, 07-30-2002 07:04:27  
Well Salmoneye, that is a cold reading. I realize the resistor is designed for a little more voltage cold, but it still never drops below 4 volts when checked hot. I'm leaning toward the original resistor. What do you think?



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Phil (NJ-AZ-SK)

07-31-2002 11:42:36




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 Re: Re: Re: Re: Re: 12 volt coil voltage in reply to Greg, 07-30-2002 10:13:20  
Greg, The 4 volts that you measure can have 2 (two very different causes. The one that most people get hung-up on is that when the voltage goes up that the Current has also GONE UP.(Simple Ohms law) but that is very difficult if a Ballast is in the circuit because when current goes up the ballast Resistance also goes "UP"

The other reason is that the Resistance of the Coil /Points/ground Dist assembly has "Increased" (normally ~ 1.0 ohm) and that this has changed the resistance Ratio.... This will result in lower total current but a higher voltage measurement across the coil.

A very quick measurement of the Voltage Drop "across" the "original" Ballast Resistor will tell you if current has gone up or down. The Normal VD = ~2.7 volts... more than 3.0V indicates increased (high) current (you may have the wrong 2nd ballast R)..... less than 2.0 volts indicates LOW current and an external Resistance that needs to be found, most likely will result in starting problems.

JMHO

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Salmoneye

07-30-2002 11:27:09




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 Re: Re: Re: Re: Re: 12 volt coil voltage in reply to Greg, 07-30-2002 10:13:20  
Dell or Claus can probably tell ya better, but IMHO, if you are not ruining points or coils on a regular basis, I would leave well enough alone.

But that is just me and I like tinkering...



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PHILIP

07-30-2002 04:51:51




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 Re: Re: 12 volt coil voltage in reply to Dell (WA), 07-29-2002 23:22:15  
I AM FIGHTING THIS SAME PROBLEM RIGHT NOW. WITH THE FRONT MOUNT DISTRIBUTOR, HOW DO YOU KNOW WHEN THE POINTS ARE OPENED OR CLOSED? THANKS. PHILIP.



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Dell (WA)

07-30-2002 05:21:49




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 Re: Re: Re: 12 volt coil voltage in reply to PHILIP, 07-30-2002 04:51:51  
Philip..... ....eaziest way I know is to watch your voltmeter and put the tractor in gear and push on the big rear tire, rolling the tractor a little bit. When the voltmeter changes one way or 'tuther (don't matter which way) you will know wheather points are open (battery volts) or closed (some lower volts), then roll the tractor back if not the points open/closed position that you want. Take your sparkies out so your not fighting compression. You can also do it, pulling on the fan belt with sparkies out in neutral gear. Watch your meter. Don't try to do it with the starter, you can't control it. Watch your meter, battery volts = points open..... ...Dell

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PHILIP

07-30-2002 07:30:51




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 Re: Re: Re: Re: 12 volt coil voltage in reply to Dell (WA), 07-30-2002 05:21:49  
MAKE SINCE. THANKS DELL. PHILIP.



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Mountainman

07-29-2002 23:07:20




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 Re: 12 volt coil voltage in reply to Clay, 07-29-2002 22:01:45  
Opinions vary as to the correct voltage but you are right on target. If you have a 12 volt front mount coil 8 volts would be just about right.
A couple pages back there is a post with a link to 12 volt wiring diagrams if that would be of help to you.

Mountainman...CA



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