"BALLAST RESISTOR IS YOU FRIEND"

I first composed this in response to Bruce's post:
http://ytforums.ytmag.com/viewtopic.php?t=520622


But then as I kept expanding, I decided it need it's own stand alone posting with a new Subject line.

I expect that some of the major reasons the round can coils hold up better is that the oil is in intimate contact with the heated wires and conducts to the high-thermal-conductivity metal can, allowing heat to be moved from the wires to the ambient air. Whereas, the old square can units were encased in asphalt/tar/pitch (not the same intimate contact that oil provides) and whatever heat conductivity it had, it has no where to conduct it to other than a very low conductivity plastic case. Thermally conductive epoxy (if the Chinese spend that kind of $ on them today) would help, BUT the thermal path is still blocked more or less by the plastic case.

Take the IC14SB with no resistor and look at it.
14.7v/3.25 ohms=4.5Amps Then running, ~(4.5A X 0.33)=1.5Amps
Pwr steady state=65.8Watts {11.5W}
Pwr running=7.3Watts {1.3W}

Compare to the original FORD sq can numbers in {}

NOW THAT TELLS YOU WHAT THE RESISTOR IS FOR! It keeps the heat out of the coil! (The IC14SB is running at 4.5A & the Ford at 4.8A in these comparisons.)
Since spark energy is proportional to the current squared, there won't be a lot of difference in the two. (Time constrains the inductance).
The RESISTANCE PROVIDES OTHER BENEFITS AS WELL, such as shortening the coil charge up time and stabilizes current over temperature as the coil heats up and its winding resistance increases. Were it not for this stabilizing effect of the external resistor, the coil energy would decrease to 56% of its cold start value, just due to the temperature induced winding resistance increase.
Compare that to the original Ford design with external resistor and you will find the over the same temperature rise from 68F to 200F, it is still producing 90% of its cold start value.

I should name this posting, "BALLAST RESISTOR IS YOU FRIEND", despite all the trouble folks seem to have in using them properly.

So, someone will ask why the IC14SB popularity? Well, I would say ease of use. It is a no-brainer, even if it sacrifices output over temperature and apparently it can handle the additional heat load that it generates. They work & they sell.

Overall, the same heat is there if the battery voltage and coil current is the same........the resistor heat is just transferred from the resistor to inside the coil when no resistor is used & adds to the coils own heat as with the IC14SB.

This same analysis applies when comparing the use of a 6v sq can coil and a so called 12v (2.5 ohm) sq can coil (either one operating on a 12v system).
If properly ballasted, both will provide about the same spark energy (remember, 1/2 x L x I*2) as current can be made equal. But the 6v coil will be running much cooler at ~ 5X lower power (heat) than the so called 12v sq can coil. Compare 11.25Watts vs 56.5Watts in stalled condition and 1.3Watts vs 6.5Watts running.

I do not wonder why folks have so much trouble with the so called 12v (2.5 ohm) sq can coils on 12v systems. It is clear to me, and I hope to others now.
Thank you and good evening,
JMOR

A 30 -40 year old piece of special testing equipment. As you discovered, a battery charger won't do it. I'm surprised that you didn't toast the coils as well.

Coil problems are difficult to diagnose. For starters, round coils are pretty robust & square coils aren’t, but neither one will hold up to a poorly done 12v conversion that allows too much current to the coil. There are a few ways to see if a coil is bad, but it’s not possible to determine if a coil is good w/o some expensive testing equipment. If you detect a dead short or high resistance in the coil w/ an ohm meter, it’s bad. If it’s cracked, it’s bad. If a sidemount coil w/ battery voltage to the primary will not jump a ¼” gap from the secondary wire to the block, it’s bad. But, here is the hard part: even if you do not detect a short, even if it will produce a spark, even if it’s not cracked, that doesn’t mean the coil will work when it’s hot & under a load. So, it’s a process of elimination. If the tractor starts & runs fine for 30 minutes or an hour then cuts off & refuses to re-start, and you checked for spark at the plugs & it had no spark at all, AND you jumped the ignition switch and the resistor (if it has one) that’s a good sign that you have a bad coil. Let it cool off, restart it & if you have a good spark, odds are it’s a bad coil. But, even then, you might end up w/ a spare coil on the shelf.
50 Tips

Mike.......you ask......."what is the secrete to testing coils?......would you believe on the tractor with my calibrated tester? Seriously! Take enny sparkie and bend the side electrode out for a full 3/16" airgap. Clamp the sparkie shell to a convenient bracket. Plug enny sparkie wire to the top of the calibrated tester.

With the tranny in NEUTRAL and ignition switch ON; standing on the ground, crank yer engine while watching yer calibrated tester for sparkies. Are they blue-snott hot or wimpy yellowish-orangish poor excuses??? or no sparkies at all???

You can NOT test sparkie coils with ohm-meters or volt-meters. They ain't sensitive enuff. It only takes a couple of turns to be shorted out by melting insulative tar and you ain't gott NO SPARKIES.

BTW, ALL squarecan ignition coils ABSOLUTELY need the "infamous ballast resistor" even on yer bench lash-up. Its the LAW; Ohms Law. Otherwize you either burn out the coil or the substitute battery charger. Electronic lessons, eh?

FYI, my eazy starting 6-volt 52-8N will jump a full 3/8" gap. It can be done. ......Dell, yer self-appointed sparkie meister

I love it when you guys talk technical!

:lol: 8)

es

(quoted from post at 22:55:03 08/20/09) I love it when you guys talk technical!

:lol: 8)

es

Click to expand...

I got it all figgered out now!!
(Yeah, Right)

Wow! Chris needs to get to work! The mix & match & cross polarization of post is amazing! I an a bit accustomed to the disconnect between Classic & Modern, but now it is BOTH! :roll:

What you REALLY need is whatever total resistance is required to yield 3.5 to 4amps thru whatever particular coil you have, as measured with engine stalled & points closed. Forget everything else you have read, heard, or seen. An 8n10306 may be several values depending on where you bought it, who from, and what day ....they have been found from 0.5 to 1.0 to 1.6 to???

Dimmer.......you read but don't understand.

A little "history" for you. Way back innna 1996? the FIRST versions of the 12-volt squarecan ignition coil hit the market. Touted as a 12v-coil, they were being returned to mfgr as FAILED in short time. Why? 'cuz they were true 12v-coils and the popular Delco 10SI is a 14.7v alternator. (14+ volts are necessary to charge 12.6v battery) ...ie... OVERHEATING and melting the insulative tar.

They soon were enclosing a little piece of toilet paper printed in 6-languages 'cept 'mercum (who reads instructions, eh?) telling users to add a 0.5-ohm current limiting resistor of some unknown part number. Which tractor parts stores don't sell ennyways.

Since RadioShack was generally everywhere, I told them to buy R-S pn: 271-131 (2-pack of 1-ohm 20-watt resistors) and twist the leads together. Thus creating a 0.5-ohm 40-watt current limiting resistor. Its the LAW, Kirchhoff's Law. (equal value resistors in parallel is 1/2 the original value, and the watts are summed) Isn't that amazing?

As fer p/n: 8NE10306......."(Must use 8NE10306 resistor in wire between ignition switch and coil to prevent burning up points or coil. Not included. Sold separately.)".......guess what? That is a 0.5-ohm ceramic resistor that is the equivalent of R-S 271-131. (small picture)

Then you gitt confused ......"Also have read that you only need the A8NN12250B Junction Block resistor".......yes, that is the NECESSARY MANDATORY "infamous ballast resistor" for either the 6-volt or the 12-volt squarecan ignition coil. (large picture) .....DON'T ARGUE!!!!

Now do you understand??? ......respectfully, Dell, yer self-appointed sparkie-meister

Thanks Dell, I'm a lot closer to understanding. Reading depends on the year of the advice.

So on my 9N using a 12v square coil I need both the ballast resistor and the 8NE10306?

Dimmer.......you wrote.......

"Part 9N12024-12Volt - 12V IGNITION COIL, for FRONT Mount Dist. 9N1202412V---12 volt square ignition coil.

For 9N, 2N, & early 8N (prior to s/n 263843) with FRONT mount 9N12100 distributor. For systems converted to 12 volt.

umm? what does this say????......(Must use 8NE10306 resistor in wire between ignition switch and coil to prevent burning up points or coil. Not included. Sold separately.)" ......PAY ATTENTION!!!!

Both JMOR and Bruce correctly use math to prove the necessity of the "infamous ballast resistor". And I agree, you NEED the mandatory "infamous ballast resistor", whether 6-volt OEM or modern 12-volt squarecan coil. But too many of you shadetree "bubbas" FLUNKED. You can lead a horse to water but you can't make'm calculate ......respectfully, Dell

Dell,

Pardon me for being so stupid and you for pointing it out.

(quoted from post at 15:14:46 08/21/09) Dell,

Pardon me for being so stupid and you for pointing it out.

Click to expand...

Well, Dimly lit, I can sympathize with you, because I have read these last several posts more than once & despite all the words, I guess I must be a retard too, since to the best of my reading skills, I too do NOT know whether DELL said use BOTH or not. I can not see the word "both" , nor do I see anything such as 'series the two resistors', etc.
I think the two in series is what he wants you to use, but I ain't the guy to put words in his mouth.

As I said before, since the coil values and apparently the 10306 marked resistors are all over the map, I measure and select for 3.5 to 4amps at 14.7 volts.

JMOR,

I made note of your previous post of the 3.5 to 4 amps. I just need to get the time to check both my tractors. I've had the tractors for 19 yrs. The 1939 9N was a 6v converted by a friend about 6 yrs ago to 12v system with an alternator and a 12v square coil. It runs great. The 1940 9N was a converted 12v with a generator and a 12v square coil that I just switched to a 12v alternator. I just looked and neither one is using the ballast resistor to coil connection, only the 8NE10306 resistor. I've got a spark problem with the 1940 tractor and will be using some test methods from previous posts read to check out the distributor. Just wondering about how the wiring and resistor SHOULD be. I've done a lot of work on both tractors over the years and this has me stumped.

If you have specific questions, just ask.

I am stupid! I read your banter on resistors 5 times and still can not figure out if I need 2 resistors or not. I have a 9n converted to 12 volt by the previous owner. the square coil did not work. I installed a new 12 volt coil. It now runs.
Do I need a A8NN122508 resistor followed by a 8NE10306 resistor?
A clear answer without all the technical banter would be greatly appreciated

Larkdad

Larkdad, it appears that you directed your question to Dell. If that is the case, I will stay out, but should you question be an 'open' question, then I can't give a responsible answer without knowing exactly what 'new' coil you have along with it's primary resistance value.

Larkdad........dunno how I can say it more plain. Either the OEM 1.2-ohm 6-volt squarecan ignition coil ...or... the new modern 2.5-ohm 12-volt NEED the mandatory "infamous ballast resistor" .....NO ARGUE..... Understand???

Since I flunked mind reading, (just ask my ex-wife of 32-yrs) I can't guess whether you need an additional 0.5-ohm "safety" resistor or NOT ...or... a 12-to-6volt converting resistor (the 8NE10306 is NOT a 12-to-6volt converting resistor)

Both JMOR and Bruce have demonstrated mathematically how to determine iff'n you need that extra "safety" resistor by reading yer 20% accurate dash ammeter.

Unfortunately, you can NOT simply measure the coil winding resistance with consumer grade ohm-meter. (its a technical thing) But amazingly enuff, the $20 hardware store voltmeter is more than accurate enuff.

Just read the coil terminal volts with the points closed. (hint: points open reads battery volts) The OEM 6-volt squarecan coil should read about 2.5-3.0volts. The modern 12-volt squarecan coil terminal should read 9-11volts. As you can see, its NOT CRITICAL. .......respectfully, Dell, ret Elect Engr

I"m open to all
The coil I have has no markings.Paperwork (from testerdays tractor) says ford coil 12 volt replaces 9N12014-12V. It was imported all the way from Red China.
Do i install both resistors ? just one? which one? if both how wired?

(quoted from post at 07:58:18 08/22/09) I"m open to all
The coil I have has no markings.Paperwork (from testerdays tractor) says ford coil 12 volt replaces 9N12014-12V. It was imported all the way from Red China.
Do i install both resistors ? just one? which one? if both how wired?

Click to expand...

Just use the 12250 wires just as stock tractor was wired.

larkdad.......dunno how more plain I can tell you. I don't care where yer squarecan ignition coil was made. I don't care what the voltage of yer tractor is. ALL squarecan ignition coils NEED the mandatory "infamous ballast resistor". UNDERSTAND???

And lets make a WAG, (WAG = wild azz guess) since the box the coil came in sez 12v, be BOLD and DARING and assume it is a 12v-squarecan coil that need the mandatory "infamous ballast resistor" located on the backside of yer dash panel under the amp-meter.

And iff'n it needs the 0.5-ohm safety resistor, (which I doubt) resistors are like flashlite batterys ...in series... and it don't matter which one is first or last. Just gotta be ennywhere between yer weaksistor ignition ON terminal and yer squarecan top terminal. ......respectfully, Dell

I think I understand now. It appears the person who did the conversion to 12 volt disconnected the original resistor ( infamous ballast resistor)and just used the 0.5 ohm safety resistor. The original resistor is still there. I will reconnect it and see what happens.
I have 2 9N tractors. The 12 volt tractor has the block serial number as JC 035. Is that an original engine/serial #? Tne dipstick for the transmission/hydraulic oil is next to the oil fill. On the other tractor serial # 55267 the dipstick is on the cover plate opposite the pto lever.

Thanks for the help
Lou

Lou......ALL 9N/2N's engine s/n start 9Nxxxxxx. Howsomevers; Ford also sold the tractor engine for industrial purposes; irrigation pumps; OIL field pumps; railroad refrig coolers; Pullman air conditioners; portable electric light gennys; heck, even early WW2 Jeeps had them. Many had magnetos for ignition and arm-strong starters. (hand cranks) I haven't gotta clue what yer "JC 035" means. Engine gutts are all the same. (rings, bearings, etc) just the electricals and fuel systems could be different......Dell, the NON-authority

I guess its a frankenmotor

Lou

Now you know that silicon diodes dont take hi voltage well.The chargers can be repaired.Take a look at an ignition diagram and you will see that the spark went though went thru the diodes.I use a nicad battery that has open top straps so I can use 4 volts for testing coils.The diodes in small chargers are about the size of an aspirin tablet.They have a voltage rating of 100 volts.You hit them with 10000 volts.This is what happens when lightning strikes the power lines.If you left the chargers plugged in you would have seen smoke and flames.The circuit breaker used in chargers will not protect against shorted diodes.They open if a battery is connected reverse polarity.