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Show Parts for Model:

ignition resistance

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Author  [Modern View]

08-11-2010 09:49:16

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I'm redoing my wiring harness on my 1950 8n side mount 12v with 3 wire alternator. I have the IC14SB coil.

My question is about the resistor on the wire to the coil.

I read here, "REAL 12-volt ignition coil that uses NO RESISTOR. NAPA IC14-
SB is recommended" ( I think from Dell)

On another site I read, ". The ignition circuit is a balancing act between having enough resistance to protect the coil but not so much resistance that we no longer have a good hot spark"

My question is, do I need a resistor? There is already one attached to the left side of the block. It is white and has two push on connecters. It was on the tractor before I bought the new coil. If I do need a resitor or don't how do I know? What are the pros and cons and testing methods to determine if needed or not. Thanks guys!!

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08-15-2010 17:41:43

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 Re: ignition resistance in reply to soundguy, 08-11-2010 09:49:16  
Quoting Removed, click Modern View to see im gona try to be a bit more polite than you (but it aint easy) thanks for your input for what its worth.

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08-11-2010 19:15:58

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 Re: ignition resistance in reply to Sparks, 08-11-2010 09:49:16  
That other site provided you with a lot of meaningless verbage. There"s nothing in that statement that will help you understand the primary igniton circuit.
Most of these tractor ignitions systems are designed for about 4 amps max primary current. If you have a 6v system, that means the total primary reistance should be ~ 1.6 ohms. I have a 6 v coil that I measured the resisitance of and it was 1.6 ohms on the primary side. I have a 12 V coil and it has 3.2 ohms of primary resistance. So either one when installed in the appropriate primary circuit will provide a nominal 4 amps of primary current. That"s why your IC-14SB coil is called a 12V coil. It"s used in a a 12V primary ignition circuit and DOES NOT REQUIRE A RESISTOR. And that"s what Dell is telling you in his usual way.

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08-11-2010 18:24:01

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 Re: ignition resistance in reply to 36 coupe, 08-11-2010 09:49:16  
You havta read the stuctions that came with the coil,,, some of'em do use a resistor,,, flamethrower that is,,, the IC14SB that i will pat myself on the back for cuzz I am the original poster that recommended it is really a 14V coil so no resistor needed,,, it it were a 12V coil a resistor would be needed to handle the extra 2 volts under charging conditions...

IC, Ignition coil,,, 14, 14V,,, SB cheap NAPA chit to compete with the other cheap chit out their.... its a consumer thang.... 20 million mexkins demand it...

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08-11-2010 13:53:54

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 Re: ignition resistance in reply to HCooke, 08-11-2010 09:49:16  
Quoting Removed, click Modern View to see i have the same tractor as sparkes but my 12-v coil is a flame thrower that i got from here, can i remove my ceramic ballast resistor?

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Dell (WA)

08-11-2010 16:35:54

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 Re: ignition resistance in reply to gutterman, 08-11-2010 13:53:54  
gutterman.......again what part of use NO RESISTOR don't you understand??? A 12-volt coil is designed to be used with 12-volt electrical system, flame-thrower or not.

But heres the deal with a "flame-thrower" and the UNNECESSARY ceramic ballast resistor. It will output about 40-kilovolts of sparkie power with 12-volts. Great for jumping 0.065" (1/16") gapped plugs or oil fouled plugs. When you cut the volts down with the UNNECESSARY ceramic resistor, you probably have about 25-kilovolts of sparkies. You need about 15-kilovolts of sparkie power to jump regular clean 0.025"-gap sparkies. So you have plenty of sparkie power for even worn fouled plugs with yer resistorized flame-thrower.

Why would you want 40-kilovolts of sparkies??? WIDE GAP sparkies sparkle for eazier starting and smoother idle and still will sparkle for 8,000-rpms racing engine.

Biggest problem with 40-kilovolts is the insulation of the sparkie wires. It hazzta be fresh and soft and limp and copper stranded. OLD DRY CRACKED sparkie wire will have them lazy sparkies dancing on the outside of the insulation 'stedda' jumpin the gap inside the cylinder head. ......HTH, Dell, yer self-appointed sparkie-meister

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Dell (WA)

08-11-2010 09:57:31

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 Re: ignition resistance in reply to Sparks, 08-11-2010 09:49:16  
Sparks........what part of ""REAL 12-volt ignition coil that uses NO RESISTOR. NAPA IC14-
SB is recommended"......don't you understand??? That is ALL you need for the 5-nipple sidemount dizzy and 12-volt conversion.

Ennythang else you've read about resistors is directed to the weird 4-nipple dizzy and squarecan ignition coil. Which you DO NOT HAVE!!! ........respectfully, Dell, yer self-appointed sparkie-meister

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08-11-2010 10:02:37

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 Re: ignition resistance in reply to Dell (WA), 08-11-2010 09:57:31  
hmm, wonder if I had a round can 6V on there before?

I understand it now oh great Sparkmeister. I bow to your extensive knowledge. thanks!! Fast response too. You guys are awesome!

I'll have updates after my Friday afternoon shadetree pasture mechanic-ing. Hope I can it started and avoid a heatstroke in this Oklahoma heat wave.

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08-11-2010 11:14:11

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 Re: ignition resistance in reply to Sparks, 08-11-2010 10:02:37  
it's very likely that the coil you had on there before was a 6v style, which is why the resistor is/was in line. The ic14sb needs no resistors.


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08-13-2010 22:06:04

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 Re: ignition resistance in reply to soundguy, 08-11-2010 11:14:11  
Well guys I took off at noon today, packed up my tools and headed out to the farm where my 8n was sitting in a nice shady spot I had towed it to after it died. I had been mowing for a couple hours a few weeks ago when it started running rough, slowed down, died, and then wouldn't restart.

Went out with a new coil, points, condenser, rotor, dizzy cap, wires, plugs and put it all in. Looked over the old girl and saw the wiring harness was a mixed up jumble of dead end wires, splices, tape, bare wires and just didn't look right. I was checking the oil and hit a bare wire and it sparked. I figured maybe I ought to go ahead and change the whole wiring harness. Got a new wiring harness with a diode for the 2 wire alternator, an new ignition switch, and a terminal block.

So I went out today in 104 heat with a gallon of gatorade and a plan. I replaced the wiring harness and put the freshly charged battery back in. ---no sparks. What a bummer. Still had lots of sun so I pulled the secondary wire from the coil off the distributor. Cranked but no spark. I was lost, all the wires were new, plugs, coil, points... everything was new. I wasn't going to give up.

My voltmeter ran out of batteries so I was kinda stumped.

Can you guess what I did to make it work?

I took the bushing and bolt out of the side of distributor where the wire from the coil comes in. Brushed it all clean with a wire brush. Put it back together. Cranked the starter and the coil was sparking. Put the dist. back together and i had one of the#4 plug out but hooked to the wire. I cranked it to see if I'd get a spark when grounded on the manifold. I got shocked! then the tractor started right up. First crank, no choke. It ran pretty good on three cylinders. I turned it and put the plug back in. Started right up and ran better than it ever had. I only had he tractor since the spring.

So, thanks to this forum I got the info to get this fixed. I remembered reading about someone else who had the coil wire to the points giving them a problem and I think that was the problem but all the other new stuff sure helped and now I have some spare parts.

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08-14-2010 07:36:49

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 Re: ignition resistance in reply to Sparks, 08-13-2010 22:06:04  
yep.. no power was getting to the points. many times that feed thru insulator shorts as well.

glad you got it fixed.


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08-14-2010 07:47:38

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 Re: ignition resistance in reply to soundguy, 08-14-2010 07:36:49  
Yup... as Sounder said that pass-through terminal is a COMMON source of no-spark problems that stump guys all the time... either shorted or a poor connection or broken copper strip (opens).

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