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Ford 9N, 2N & 8N Discussion Forum
Show Parts for Model:

1 ohm 10 watt resistors in 12 V system(attn: Dell)

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Gary Prestridge

11-11-2004 15:30:19
68.222.99.29



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Now that I have done this, what is it suppose to do? Help prolong coil and point life???




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yes . . . Dell (WA)

11-11-2004 18:01:26
172.199.154.54



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to Gary Prestridge, 11-11-2004 15:30:19  
Gary..........I've explained this secret trick 1/2 ohm current limiting resistor scheme for the modern 12 volt squarecan ignition coil many times. (it seems at least once a week, grin)

To start with, you need about 15,000 volts to jump yer 0.025" sparkie gap under compression. This is why you just can't take a sparkie outta the engine and say "lookie, I gotts good sparkies, whoops that bytes". The effects of compression makes it harder for the sparkies to jump the gap. ...but... iff'n yer sparkie will jump a 3/16" gap in normal air, yep ya gotts good sparkies alright.

But what does this have to do with ignition coils? Well first off, yer electrical system is 6 or 12 volts and while you can arc-spark with a short circuit, your direct current (DC) battery will never make sparkies under compression. So you use a step-up transformer scheme ...except... transformers don't like direct current because the transformers magnetic iron core saturates and doesn't couple the direct current primary to the secondary. That is majorly profound, and is why alternating current works in transformers.

So why do ignition coil transformers work on direct current? ...because... they want that saturated core's magnetic field ...to... COLLAPSE when the points open!!! The magnetic field's collapse it very sudden and induces the stepped up sparkie voltage in the secondary, which it switched to the correct sparkie by the rotor.

So where are we going with this? Its the electron's flow thru coiled wire that creates a magnetic field. The iron core captures the magnetic field. ...but... the strength of the magnetic field is dependent upon ...are you ready for this?... AMPS!!! ...but... the problem with amps is resistance, which causes HEAT.

So to reduce resistance, increase diameter of wire ...or... shorten the wire making the turns of the coil of wire. ...but wait... its the turns of wire that make the magnetic field strong so shortening the length of wire in a coil is not a viable option to a coil designer. So there is only so much room for all the turns of wire in the squarecan coilbox to increase the magnetic field.

So when they designed the modern 12 volt squrecan frontmount ignition coil, they boo-boo'd. They designed the primary coil turns (and subsequently it total resistance) for standard 12.6 volts of a wet-cell battery. (+10% to charge the battery from whatever yer chargin' it with) ...BIG PROBLEM... is the common in-expensive and popular Delco 10-SI 12 volt alternator internal solidstate voltage regulator is designed for 14.7 volt output and automatically regulates the current pumped out to fill the battery and run all the electricals.

So there you are, pumpin' 14.7 volts into a 12.6 volt coil. Wanna guess whats gonnna happen? TOO MANY AMPS is what is going to happen. Ohms Law still rules (after all these years) So your nice modern 12 volt squarecan ignition coil is baking in its own current and OVERHEATING and melting its internal insulative tars and eventually shorting out some of its windings and causing weak sparkies and hard running. But'll start just fine the next morning after cooling off overnight until it warms up and melts again.

Enter my secret trick current limiting resistor scheme for the modern 12 volt squarecan ignition coil. Back about 1997/8 right after they introduced the 12 volt frontmount coil, (greatest thing since sliced bread) Ford tractor converters (and Ford is the "only one" that uses this squarecan ignition coil) were overjoyed that someone was paying attention to the needs of the tractor marketplace. 12 volt ignition coil, wow, don't need those 12 to 6 volt converting resistor to go with the "infamous ballast resistor" to run on 12 volts, so simple, eh? And then the coil mfgr started getting returns and complaints about coil crapping out...not good!!!

So the coil company (there is only one that I know about) started putting a tiny sheet of toilet paper in the box printed in 6-different languages 'cept 'muricum, recommending using a 0.47 ohm 10W series current limiting resistor to keep from burning out their new modern 12 volt squarecan ignition coil. (instead of changing the internal construction to reduce current draw and subsequent OVERHEATING) But who reads the instructions ennyways, eh?

And thats the long story of my secret trick current limiting resistor scheme for the modern squarecan 12 volt ignition coil used on 9N/2N/8N frontmount ignitions. People can generally get RadioShack p/n 271-131 1-ohm, 10 watt 2-pak resistors and twist the leads in parallel to create a 1/2 ohm 20 watt current limiting resistor. I'm an Electronics Engineer, so I know where I can get real 0.47 ohm resistor, but know what? don't matter, 0.47 is equivalent of 1/2 in the electronics world.........respectfully, Dell, a 12 volt advocate for the right reasons

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Jim Cox

11-12-2004 10:26:51
66.119.27.162



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to yes . . . Dell (WA), 11-11-2004 18:01:26  
WELL SAID DELL!

But why would someone think you need a post-hole digger?? ( PHD )

Sorry, couldn't pass that one up. From my days as an entertainer in Branson, MO

Jim Cox



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Hey Dell,,,,John,PA

11-12-2004 07:33:36
69.72.10.245



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to yes . . . Dell (WA), 11-11-2004 18:01:26  
Sounds like you have finished another discourse.
Have you recently reviewed the requirements for a PhD? (grinning).. John,PA



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Gary Prestridge

11-11-2004 18:36:11
68.222.99.29



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to yes . . . Dell (WA), 11-11-2004 18:01:26  
You are something else....to put up with so many of us morons and still take so much time and effort to help us out over and over..Thanks for the very detailed explanation,,You can believe I will keep it for future.....I got my Dell secret 1 ohm 10 watt resistors installed and cranked it this afternoon....as you suggested I put it on the original ballast resistor board in place of the original resistor thing..I just have to go back and make it look a little neater..Thanks again..Now let me think..What can I worry Dell with next????????

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souNdguy

11-12-2004 21:25:06
12.77.214.135



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to Gary Prestridge, 11-11-2004 18:36:11  
That would be 'secret 1/2 ohm 20 watt resistor.. '


Soundguy



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Gary Prestridge

11-13-2004 13:19:23
65.12.38.33



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to souNdguy, 11-12-2004 21:25:06  
SSSSSHHHHHHHH.....don't tell anybody////......Don't worry, on other forums I visit they don't have a clue...



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KyJames

11-11-2004 17:06:13
69.139.121.172



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to Gary Prestridge, 11-11-2004 15:30:19  
Hi Gary..

It's been a year or so since I posted .. found some time on my hands and decided to drop in..

I got to thinking about this changeover You did and thinking I need to do it myself..I believe what will be found is the alt starts charging immediately , rather than having to race a cold engine.. Right now on mine . I having to over ride the governor to get the alternator charging

I could be wrong though

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Gary Prestridge

11-12-2004 03:15:56
68.19.173.126



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to KyJames, 11-11-2004 17:06:13  
Ky, thanks and good to see you drop in. I have worried these folks a lot over the last several months. Have replaced rear seals, lift pins, carburetor, distributor, wires, plugs, changed to 12V, new manifold and exhaust, new front pivot bushing, new front pulley..so you can see I have pretty much had it apart from front to back over the last 4-5 months and as you know you always run into more than expected..Everyone has been very helpful...If you hadn't already read it, read Dells book he wrote in response to my question...makes sense, and in a nut shell the resistor protects the coil...Does yours currently have the 12V system? and are you running a 6V or 12V coil? Thanks for the reply.

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KyJames

11-11-2004 17:12:14
69.139.121.172



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 Re: 1 ohm 10 watt resistors in 12 V system(attn: D in reply to KyJames, 11-11-2004 17:06:13  
quote from Dale..___"""""""secret trick 1/2 ohm 20 watt current limiting resistor.''''''

I remember that copied it and then the old computer crashed.. time to check out the archives again



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