8N Coil Facts according to TISCO. Dell?

After my recent ignition problems with my 49 8N front mount distributor with a 12 v conversion by previous owner I have decided to try and get to the bottom of the famous ballast resistor PN 12250, and the 8NE10306 resistor used with 12V conversions on the market today. I now know why there is so much confustion out there regarding resistors and coils.

I contacted a few suppliers of 12 V conversion kits and asked them the following questions;

Q: What type coil do you provide for a Front mount distributor in your 12V conversion kits? Is it a 12V or 6V coil. If it is a 12V coil does it have an internal resistor?

A: All 12V Coils produced for Front Mount Distributors do not have internal resistors.

They followed that by saying that only 12 V coils produced for 8N side mount distributors are available with interal resistors or without internal resistors. They explained this is where a lot of confusion regarding 12 V conversions lie.

Q: I asked, "does your 12 V conversion kit for a front mount distributor include the 8NE10306 resistor (12 V to 6 V resistor)? Is it included in 12 V conversions that use 12 V coils? Is it included in 12 V conversions that use 6 V coils?

A: The answer was Yes & Yes! The 8NE10306 resistor is used and supplied in front mount 12 V conversion kits regardless of the coil supplied!

Q: How do utilize the OEM Ballast resistor in the circiit?

A: Leave the OEM Ballast resistor PN 12250 in place and wire the 8NE10306 Resistor in series with it. This holds true for Kits supplied with either 12 V or 6 V coils. They did mention that if you have a 12 V front mount coil you could safely only use the 8NE10306.

Field Tests

I purchased both the Infamous ballast resistor PN 12250 and a 8NE10306 resistor and performed the following tests:

1. With only the 8NE10306 using a 12 V front mount coil I read 13 V at the coil with the points open, and 6 V at the coil with the points closed. 6 V at the coil with the points closed definately satisfies the criteria of the 12 V coil manufacturer requiring less than 13.5 V supplied to it. The engine ran smooth and idles perfectly. Although 6 V at the coil does not satisfy the criteria if one is using a 6 V coil.

2. I hooked the infamous ballast resistor pn 12250 in series with the 8NE10306. The 8NE10306 is wired between the infamous ballast resistor 12250 and the coil (if that matters). With the points open I read 13 V at the coil. With the points closed I now read 4 V. The engine ran smooth and idles perfectly. This suprised me due to the low voltage being supplied. The 4 V definately satisfies coil voltage requirements for the 12 V an 6 V coils.

Comments:

If manufacturers of 12 V coil kits are requiring you to use both resistors regardless of the coil (6V or 12 V coils) supplied with the kit, the only benefit I see in purchasing a kit with the 12 V coil is that you can get by with only the 8NE10306 resistor. I wired my 49 8N with both resistors in series as per instructions the obvious advantage is that I can run either a 12 V coil and a 6 V coil with this set up. I am running a 12 V coil and it runs fine. I also tried a 6 V coil I had and it runs fine with it as well. It started first try this morning even a 2 degress below zero.

I hope the information helps someone out there trouble shooting an ignition problem.

Hec

Hec, The "Original" 12V coil would not work in this situation as its Primary resistance was >3.5 Ohms. This would mean that a voltage reading of 4.0 Volts is ~1.14 Amps. That is not enough current (1.14 amps).

I think they may have changed the Spec's of the 12 volt Coil 1. measure the Ohms of the Coil (close is OK)

2. Measure the "Out of Circuit" Ohms of Each Ballast R

The Ballasts operate on Current.. period.. I would guess that the Coil you have is ~1.25 Ohms
or very close to the Original (1.0) 6 Volt.

JMHO

Heres the deal. Straight 6 volt battery volts, don't make enuff sparkie to jump a 0.025" gap. Transformers can change low volts to high volts, BUT transformers don't like the direct current that a battery puts out. Because once the current has flowed thru the winding creating a magnetic field, nothing else happens, even though the current (amps) is still flowing. Transformers work because of magnetic field theory. By constantly changing the magnetic field strength or polarity by changing the primary voltage, the secondary voltage responds appropriately.

BUT here it gets tricky, ignition coils work because your ignition points OPEN and the magnetic field COLLAPSES almost immeadiately. That sudden collaspse is what generates the sparkie in the secondary. And if done at the right time and place, you get your engine to run.

RIGHT NOW, you have a "pristine" ignition system with extremely low ohms to impede the flow of electrons (amps) to make a saturated magnetic field in your ignition coil to make EXCESS SPARKIES to jump the gap. Sparkies are going to jump the gap at a predetermine voltage and will ALWAYS jump the gap at that voltage. If'n you have excess sparkie volts, so what? its gonnna jump ennyways.

But what happens after a few years of operation? Your sparkie gap erodes wider and that takes more volts to jump. Your sparkie core and sideground get surface resistance as a natural by-product of ignition, and that takes more volts to jump. Your sparkies like to jump from sharp point that gets eroded and rounded off, and that takes more volts to jump.

Also what happens to your ignition points after a few years of operation? The very contact surfaces get a surface resistance that reduced the coil primary current (amps) flow. Reduced amps mean reduced coil magnetic field which means reduced sparkies. This is all natural and you can't do anything about it.

Now your needing more sparkies to jump the worn gap and you're making less sparkies due to worn points, WHATS going to happen when you intentionally add MORE RESISTANCE? in the form of 12 to 6 volt converting resistor 8NE10306 and "infamous ballast resistor" 9N12250 to a coil designed to run on 12 volts?

I submit that you've drawn an incorrect conclusion that 4 volts on a 12 volt coil is adequate because the lable sez: "do not use over 13.5 volts" and your current pristine ignition system allows your new engine to start and run on a 12 volt system with just 4 volts at the coil terminal.

Your voltages are ballpark correct for the resistors you used ...BUT... your understanding is wrong. NO RESISTORS to cut the volts on a real 12 volt coil, understand?

Howsomevers, I do advocate a 1/2 ohm 20 watt CURRENT LIMITING resistor made from 2 1-ohm 10 watt resistors in parallel; ref: RadioShack p/n 271-131 twinpak. (or eqv) Your 8N10306 is 3-times too much resistance..... ....perfesser Dell

I thought while "archive diving" I read a piece where you stated the infamous ballast resister (BR)that Henry Ford designed should be able to limit the coil voltage just enough to protect the new square can 12 volt frontmount coil??

It stands to reason (in my electronicly challenged pea brain) that if the BR can limit a 6 volt battery to 4.0 volts at the coil, then it ought to be able to limit the 14.2 volts put out by an alternator down to around 12.2 volts; enough to meet the recommended voltage on the new 12 volt frontmount coil.

Why go to radioshack if the OEM BR will do the trick?

Thanks in advance for responding!

-Fishy

I quote volts because most people seem more confortable measuring volts. While the real crux of the 12 volt connumbrum is the magnetic field that is a product of the current (amps) flowing thru the coil primary. We MUST LIMIT the current (amps) or the gutts of the coil will overheat and melt the insulative tars and shortout the coil primary winding and..... .whooops no sparkies.

Voltmeters are cheap and accurate and virtually foolproof. And we can "infer" the amps in the circuit by application of OHM's Law. But just trust my quoted volts and you'll be just fine..... ....perfesser Dell

I studied electronics and passed the tests on the GI bill at home with Devri Institute but to save my life I could't tell you what some of that theory was all about here 30 years later. I guess it helps if you actually use the learing in your day to day work which I don't usually.

Keep up the good work!

You even seem to have a more moderate attitude toward us "dummies" lately. :O)

Zane

So they used to include a little piece of paper (printed in 7 languages 'xcept 'mericum) that recommended using a 0.47 ohm 25 watt "current limiting resistor", and WARNING: 13.8 volts max. But who reads the instructions, eh? Its a 12 volt coil, I gotta 12 volt battery, and a 12 volt alternator, 'sposta work right? And its the devil in the details.

Problem is, only us ol'fashioned electronic engrs know where to gittem, so I recommend making you own by paralleling 2 1-ohm resistors for a 1/2 ohm current limiting resistor. Most everyone can find RadioShack, p/n 271-131, 2-pack, 1-ohm, 10 watts.

The 12 volt conversion kit people only know where/how to get the 8NE10306 conversion resistor. Which is about 3 times too much resistance and the reason Hec read 6 volts with his new 12 volt squarecan coil. OHM's Law still rules.

The reason Hec's 12 volt coil is working with a 12-6 volt dropping resistor, is because everything is new and he's not loosing sparkies (yet) from normal usage.

A normal 12 volt coil (with 1/2 ohm current limiting resistor) should read about 10.5 (11.5 max, 9.5 min) volts with the points closed and battery volts (12.6) with the points open..... ...the perfesser Dell, and 12 volt advocate for the right reasons

Amen. That is what has me scratching my head. What is the incentive to purchase a 12 V (More $$) when you could get away with a 6 V coil with the two resistor set up. One supplier did say the 12 V front mount coils are no more robust than their 6 V counterparts. Maybe there lies the answer? By the way how far North of Fargo are ya? I have a place On Lake Ottertail about 70 miles from Fargo.

Hec

Later Roland(AL)

I had one manufacturer actually fax me there instruction sheet for their kit. It sez to use the infamous ballast resistor in series with the 8NE10306 using a 12 V coil. Why would these guys want to step the voltage down so much if you only need be concerned with keeping the voltage below 13.5 V? My friend Doug Koozer of Koozer Tractor sez he wires them the same way. I know Danny in CO. has his set up with both in resistors in series and he is using a 12 V coil on his front mount. He sez he hasn't had any problems. Maybe my conclusion is wrong but I am only reporting my findings.

Hec

No, I am runnung a 6 volt coil with my 2 resistors.

Danny

Thanks for assembling all these facts into a single easily understood post. I was personally confused on this subject after spending the better part of 2 hours "archive diving".

I'm having major "cold weather--won't start" issues with my frontmount '49 N. And wouldn't you know it, I have 12 inches of snow on the ground with a 600 ft up hill driveway...argh!!

My N run's great when the temperature is warm. Right now all I get is a hit ever once in awhile, nothing strong enough to keep er going.

I had the same problem with 48 8N when I first got it. 2 things that I found that corrected my problem: dirty connections and battery cables that were too small. I took all connection loose and brightened them each with fine sandpaper and I replaced the cables with either 0 or 00 gauge. I don't remember which. You can't get them at Wal Mart. I went to an auto parts house and found the largest diameter I could find. They are about as big around as my thumb.

Good luck,
Danny

Do you suspect ignition? Carb? Try this for starters, remove the air cleaner tube at the carb and see if any fuel runs out. If it does you have a really flooded engine. Thats what happened to me. I had a sticky needle and seat and a leaking fuel shut off valve that gave me fits with it flooding. I rebuilt the carb, replaced the fuel shut off valve and that fixed that. The next problem I had was with the distributor. I had a short to ground on the little insulator where the condenser wire connects to. Check it. In addition gently stretch the little spring on the bottom of your coil. This will ensure that it makes contact with the screw that secures the condenser wire. Try jumping your ignition key switch. This too was problem I had. I found out that I was still getting voltage at the coil when I turned the key off due to a bad igntion switch. I suspect that this may have occured one night with the points closed. The result was a fried resistor. Give us more info and we can hopefully point ya in the right direction.

Hec

The first check would be to check your sparkie gap 0.025", maybe file 'em first for eazy sparkies.

The second check would be to check your points gap, 0.015. They've been known to slip..... ....Dell

I've replaced the distributer, cleaned and re-gapped the plugs, and replaced the plug wires. None of which improved the situation.

The points and condenser were new last summer with 8 hours on them so I didn't go that deep in the distributor. I also took that time to replace the shaft bushings in the DST, they were shot! I'll definately check the point gap next thing. I've also tried ether quick start, no help. I get a sputter or two and nothing.

I have a 12 volt conversion. I checked the voltage at the coil, got 3.5 volts with pts closed, and 12.5 volts with pts open. The only resister I see is the original ballast type mounted on the back of the dash panel, don't see any other in line between the coil and the coil side of the resister.

Anything else I should check? The motor does smoke some and I suspect either weak rings or perhaps bad valves...definately could use one or both..But she does run good when the weather is warm...hmmmm