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Coil resistance

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Russ NY

02-09-2000 16:05:35




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My 41 9-N has been converted to 12v for years. It had never been a fast starter and i have always felt i wasnt getting a good hot spark.The ballast resistor measures 1.5 Ohms.If i hot wire the coil it reads 1.5. With no power to it at all it still reads 1.5 across the terminals. Now when i connect the balast resistor back to the coil and turn.the switch it still is 1.5 ohms. I would think the 1.5 balast and 1.5 coil resistance would ad up to the 3 ohms i need but not so. Any help would be greatly appeciated.

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Charlie V.

02-09-2000 19:11:08




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 Re: Coil resistance in reply to Russ NY, 02-09-2000 16:05:35  
Try a Borg Warner coil P/N E40!! It has the
correct reistance already and you dont need a ballist resistor.



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STUMP PULLER

02-09-2000 18:08:12




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 Re: Coil resistance in reply to Russ NY, 02-09-2000 16:05:35  
DONT MEASURE RESISTANCE WITH THE POWER APPLIED TO THE CIRCUIT. AS ZANE SAID IT IS BETTER TO MEASURE VOLTAGES, THAN THESE LOW VALUES OF RESISTANCE. YOUR LEAD RESISTANCE CAN VARY ALOT AND FOR LOW RESISTANCE MEASUREMENTS THE LEADS COULD CONTRIBUTE UP TO .7 OHM. ANOTHER GOOD CHECK IS THE CURRENT. THE CURRENT SHOULD BE ABOUT 4 AMPS WITH THE POINTS CLOSED.



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Dell (WA)

02-09-2000 16:39:10




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 Re: Coil resistance in reply to Russ NY, 02-09-2000 16:05:35  
Russ.....

If your 9N frontmount is converted correctly, you should have about 3.5 volts at the coil/ballast connection. Then you should have an other resistor in series (just like flashlight batterys) that drops your 12 volts down to 6 volts to run your ballast resistor.

The key here is to understand what the ignition circuit should be. If you have an OEM 6 volt coil, it actually designed to run on about 3.5 volts and the ballast resistor is the scheme to reduce your original 6 volts system down to coil operating voltage (3.5 volts) Then the converter should have installed in series another resistor somewhere between the ignition switch and the ballast resistor to drop the new 12 volts down to 6 volts.

If you have 6 volts (or more) at the coil, you will be continually burning out and replacing your ignition points.

If you have less than 2 volts at the coil, you're going to have trouble starting an N-Tractor even in the summertime.

The real advantage of a 12 volt conversion, is that the starter really spins.

Sometimes a voltmeter makes a better tool than an ohmmeter.

Hope this gives you some ideas where to look..... Dell

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To Dell (WA)

02-10-2000 11:12:19




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 Re: Re: Coil resistance in reply to Dell (WA), 02-09-2000 16:39:10  
Welcome back ! TimK



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ZANE

02-09-2000 16:21:44




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 Re: Coil resistance in reply to Russ NY, 02-09-2000 16:05:35  
There are people on the board who are better with the elictronics of the N but I will try to give it a shot.
To begin with the resistance in the resistor will be the same if it is measured with power or without.What you should be measureing is the voltage drop when the points are closed in the distributor.I read a varity of voltages that are said to be the correct voltage. I think though that what you are looking for is about 3 volts at the coil when the points are closed.
This is true if it is 6 volts or 12 volts. It has long been my opinion that the ballast resistor effectively cuts the voltage in half. So it is necessary to have 2 ballast resistors in the ignition wire going to the coil to achieve the 3 volts at the coil. Any more voltage at the coil will rapidly burn the points and or burn the coil.

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DAVE

02-09-2000 18:08:44




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 Re: Re: Coil resistance in reply to ZANE, 02-09-2000 16:21:44  
I HAVE A 51 FARMALL CUB I CONVERTED TO 12V SEVERAL YEARS AGO.I DID NOT INSTALL A REGULAR TYPE BALLAST RESISTER INSTEAD I INSTALLED A LITTLE ROUND THING THAT WAS CALLED A VOLTAGE DROP.WHICH CUT THE VOLTAGE AT THE COIL BACK TO 6V.WITH ALL THE QUESTIONS THAT HAVE BEEN RAISED LATELY I GUESS IM GOING TO GO BACK TO THE AUTO PARTS AND FIND OUT EXACTLY WHAT IT IS THAT I INSTALLED.ANYWAY I HAVE NOT EXPRERIENCED ANY PROBLEM WITH THIS SYSTEM. THE THING THAT ALWAYS COMES TO MIND IS THAT I HAVE BEEN TOLD THAT A BALLAST RESISTOR DOES NOT REDUCE VOLTAGE BUT REDUCES AMPS,JUST AS THE RESISTOR IN A HEATER BLOWER MOTOR CHANGES THE SPEED OF THE MOTOR DEPENDING ON THE AMPS SUPPLIED .

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Charlie in TX

02-10-2000 13:57:34




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 Re: Re: Re: Coil resistance in reply to DAVE, 02-09-2000 18:08:44  
In a way you are both right. It just depends on your point of view. The coil needs 3 volts @ 2 amp. When you change from a 6 volt system (3 volts dropped by resistor 3 by coil) to 12 volt system (9 volt by resistor 3 by coil), you need 6 more volts dropped by resistor. If you didn't change resistor you would have 6 volts @ 4 amps in the coil. So the resistor controls both current and voltage. If you want a more technical explanation let me know I will email you.

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STUMP PULLER

02-09-2000 18:21:24




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 Re: Re: Re: Coil resistance in reply to DAVE, 02-09-2000 18:08:44  
YOU PROBABLY HAVE A ZENER INSTALLED. A RESISTOR IS USUALLY CHEAPER, BUT A ZENER WILL WORK FINE.



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