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Internally resisted N coils - Myth or reality ?

A

allenlane

Member
Just received my new coils after a failure of mine with a crack top to bottom on my 45 2N. Naturally was concerned excessive heat caused the failure. Bought a $30 internally resisted coil from Styner and and $15 coil from YT. I only have a p/n 12250 resistor mounted near the dash between the ignition and coil. Do not have a 10306 resistor. The $30 coil is advertised as internally resisted. See pic. It tested at 2.9 ohms. The $15 coil tested at 2.5 ohms. So yes, by tinkering with coil windings the $30 coil did indeed increase resistance.

After I got it all put together. I put my Fluke clamp meter on the coil wire with engine running and consistently got about 1 amp. A long way from the often mentioned coil killing 3-4 amps mentioned here.

mvphoto31873.jpg
 
No resistor in there, just wound differently.
I have to question the amperage reading.
Doesn't seem like it would run with amperage that low.
I have not tried to read the amperage with my clamp on though.
Might just be an anomaly in what the meter reads.
 

Specifications: Fluke 323 True RMS Clamp Meter
Specifications
AC current Range 400.0 A
DC current Range -

According to spec sheet for Fluke 323 your meter is not designed to measure DC amps
 
Yep, look right at the meter, the "AC" sinewave symbol is right next to the "A" for Amps.

Clamp-on meters typically only work for AC Amps, unless they are one of the newer ones with a "Hall-effect" DC Amps feature.
 
You have some confusing data/info here. The internal resistor is only in the ROUND CAN coil, not the square can coil. That's why when Ford went to the side mount distributor, the round coil was also introduced and therefore eliminated the need for the OEM Ballast resistor. Coils can be 6V or 12V. Measuring OHMS STATIC on a 6V square coil, probe #1 on terminal stud post, Probe #2 on the pigtail, polarity unimportant here, you should be seeing 1.5 OHMS ?.5 ohms. A 12V coil will show double that, about 3 OHMS STATIC. The OEM 12250 Ballast Resistor is the only resistor in the ignition circuit using the square coil. Your OHM readings indicate you have 12V square coils. The advantage of a 12V square coil is, when doing a 12V switchover job, you do not need to add the ceramic 1-OHM external resistor in the circuit that you do need to add if using a the OEM 6V square coil. The OEM Ballast Resistor must be in the circuit whether you have it wired OEM 6V/POS GRN or 12V/NEG GRN on a square coil system. BTW, I also have to chuckle when I hear of and see guys that claim they only will use the Flamethrower 45kv coils on their machines. These N's only rated about 15kv and that allows for some wiggle room on a poor ignition system. A 45 kilovolt coil isn't giving you anything more. Guys will believe whatever they wish and is how myths get started.

Now, on a front mount distributor with a square coil, the coil wire is secured on the LH (viewed from front) terminal post on the Ballast Resistor. With engine OFF, set your VOM to DC VOLTS, take Probe #1 and touch the LH post on the ballast resistor. Take Probe #2, again polarity does not matter, and touch any metal ground contact area. Turn the ignition key switch to the 'ON' Position but do not turn over engine. You should see battery voltage with points open, half that with points closed. Move Probe #2 to coil post. You should see same results. If no reading at either connection, your distributor needs to be pulled off and rebuilt or at least gone thru and tested as something ain't right, probably shorting out at some place internally.

Tim *PloughNman* Daley(MI)
 
You are making this a lot harder than it needs to be.

First, as I suspect you are aware, no automotive coil (round coil or front coil on an N) has an "internal resistor". Internal coil resistance is determined by
wire gauge and the number of turns. Higher resistance is provided by smaller gauge wire with greater turns. If the coil is marked or sold with a notice
"requires an external resistor" that simply means it has a low internal resistance and will be damaged by excessive voltage. It does not mean the coil has an
internal resistor. The difference between the 2 coils shows that they are wired differently.

Next, you have a meter issue. Your meter isn't going to read DC amps.

Lastly, you have a misunderstanding of basic automotive electronics. Basic, as in the Kettering Ignition system designed in 1911. The very first indication that
your data was incorrect was the 1 amp reading. 2.9 ohms on the coil, 1.7 ohms on the ballast resistor gets you 4.6 ohms in the circuit. At 14.5 volts from the
alternator, Ohms Law says your running current is 4.1 amps. Not 1 amp.
75 Tips
 

Well the meter could be a problem ! Guess I'll have to get a good dc meter as well. If you guys know of a good one, let us know. Just never really cared about ins and outs of auto electronics, but working on these old tractors and trucks are forcing me to get boned up on basics. Thanks for the info.


In the meantime, I'm having too much fun tinkering and my coil is not even warm to the touch after running the tractor for about an hour.
 
" working on these old tractors and trucks are forcing me to get boned up on basics"

Don't worry about it; it's pretty simple. If it wasn't, I wouldn't get it. I got a D in HS algebra 52 years ago and that was the extent of my higher math. Was a
history major in college. Barely got through statistics in grad school.
75 Tips
 
(quoted from post at 07:51:51 02/24/19)Lastly, you have a misunderstanding of basic automotive electronics. Basic, as in the Kettering Ignition system designed in 1911. The very first indication that
your data was incorrect was the 1 amp reading. 2.9 ohms on the coil, 1.7 ohms on the ballast resistor gets you 4.6 ohms in the circuit. At 14.5 volts from the
alternator, Ohms Law says your running current is 4.1 amps. Not 1 amp.
Click to expand...
Ummm, Bruce? 14.5 / 4.6 = 3.15. Typo?

Won't the open time on the points decrease the running current?
 
(quoted from post at 10:46:43 02/24/19)
Well the meter could be a problem ! Guess I'll have to get a good dc meter as well. If you guys know of a good one, let us know.
Click to expand...

If you are a Fluke man their 365 clamp meter ($200+) will measure AC/DC amperage up to 200A. With a resolution of .1A not going to be too useful for mA measurements.

TOH
 
LOL!

Looks like I can't type either! Yea,
3.15.

And yes, the actual current will be less
because of the points opening. But it
takes higher math skillsthan I possess to
figure the average current based on
dwell. ;)
75 Tips
 
(quoted from post at 14:33:10 02/24/19) LOL!

Looks like I can't type either! Yea,
3.15.

And yes, the actual current will be less
because of the points opening. But it
takes higher math skillsthan I possess to
figure the average current based on
dwell. ;)
75 Tips
Click to expand...
t is even more complicated than just dwell. When points close, the current changes from zero to max along an exponential curve.
 
Yea, the math for that is about as hard as chicken lips!

I had to learn it at 17 w/ a teacher whose first language was Ukrainian. And his second languages were Russian and German. His English was like Boris & Natasha. I
was in Army radio school before I learned the term condensator was really pronounced condensor.
 

Thanks Jesse for going easy on us folks stumbling around in the dark and sparing us that math. I assumed that amp reading(inadequate meter aside) was in the zipcode based on your info of a running current being about 1/3 or so of a nonrunning engine with key on and current going to the coil (I probably have that wrong too !). After all this hubbub, I'm not going to rest until I can somewhat accurately measure the amperage of my system. I probably should just let it go, but now I'm just too dang curious. As I sneak up on retirement, and fool around enough with tractors and cars, think I can justify a good DC amp meter.
 
(quoted from post at 18:58:07 02/24/19)
Thanks Jesse for going easy on us folks stumbling around in the dark and sparing us that math. I assumed that amp reading(inadequate meter aside) was in the zipcode based on your info of a running current being about 1/3 or so of a nonrunning engine with key on and current going to the coil (I probably have that wrong too !). After all this hubbub, I'm not going to rest until I can somewhat accurately measure the amperage of my system. I probably should just let it go, but now I'm just too dang curious. As I sneak up on retirement, and fool around enough with tractors and cars, think I can justify a good DC amp meter.
Click to expand...
n the zipcode alright. It is pretty sensitive to dwell angle/point gap. As Hobo said, most multimeters have a DC current capability. Since this is not a DC waveform, you will be measuring the average of it and really need an analog meter. I have always used an old Simpson 260.
 
(quoted from post at 12:34:15 02/24/19)
(quoted from post at 10:46:43 02/24/19)
Well the meter could be a problem ! Guess I'll have to get a good dc meter as well. If you guys know of a good one, let us know.
Click to expand...

If you are a Fluke man their 365 clamp meter ($200+) will measure AC/DC amperage up to 200A. With a resolution of .1A not going to be too useful for mA measurements.

TOH
Click to expand...

My primary job these days is a sewer lift repairman for the City of Hot Springs . I had never worked with 3 phase or diagnosed capacitors and such . 300 hp to 2 hp motors and controls . I have worked on plenty of gate operators from present to back when they were full of relays before the electronic control boards . The last year has been an exciting learning curve for me .

They furnish me a nice Fluke 324 which does everything I need at work , but you guessed it , no DC amp readings :( . I carry it with me , even home in case I get an emergency call in the middle of the night . I go above and beyond so I can usually ask for special tools and have pretty good luck getting them if it is during the budget high . I need to start thinking of a good reason I need a 365 other than I want to take it home to see what my starter amp draw is . I think starters are below the 200 amp limit on the 365 model .
 
(quoted from post at 00:13:05 02/26/19)
(quoted from post at 12:34:15 02/24/19)
(quoted from post at 10:46:43 02/24/19)
Well the meter could be a problem ! Guess I'll have to get a good dc meter as well. If you guys know of a good one, let us know.
Click to expand...

If you are a Fluke man their 365 clamp meter ($200+) will measure AC/DC amperage up to 200A. With a resolution of .1A not going to be too useful for mA measurements.

TOH
Click to expand...

My primary job these days is a sewer lift repairman for the City of Hot Springs . I had never worked with 3 phase or diagnosed capacitors and such . 300 hp to 2 hp motors and controls . I have worked on plenty of gate operators from present to back when they were full of relays before the electronic control boards . The last year has been an exciting learning curve for me .

They furnish me a nice Fluke 324 which does everything I need at work , but you guessed it , no DC amp readings :( . I carry it with me , even home in case I get an emergency call in the middle of the night . I go above and beyond so I can usually ask for special tools and have pretty good luck getting them if it is during the budget high . I need to start thinking of a good reason I need a 365 other than I want to take it home to see what my starter amp draw is . I think starters are below the 200 amp limit on the 365 model .
Click to expand...

my fluke 30 doesn't do DC either :(

but it was free, so :)
 
(quoted from post at 00:16:34 02/26/19)
(quoted from post at 00:13:05 02/26/19)
(quoted from post at 12:34:15 02/24/19)
(quoted from post at 10:46:43 02/24/19)
Well the meter could be a problem ! Guess I'll have to get a good dc meter as well. If you guys know of a good one, let us know.
Click to expand...

If you are a Fluke man their 365 clamp meter ($200+) will measure AC/DC amperage up to 200A. With a resolution of .1A not going to be too useful for mA measurements.

TOH
Click to expand...

My primary job these days is a sewer lift repairman for the City of Hot Springs . I had never worked with 3 phase or diagnosed capacitors and such . 300 hp to 2 hp motors and controls . I have worked on plenty of gate operators from present to back when they were full of relays before the electronic control boards . The last year has been an exciting learning curve for me .

They furnish me a nice Fluke 324 which does everything I need at work , but you guessed it , no DC amp readings :( . I carry it with me , even home in case I get an emergency call in the middle of the night . I go above and beyond so I can usually ask for special tools and have pretty good luck getting them if it is during the budget high . I need to start thinking of a good reason I need a 365 other than I want to take it home to see what my starter amp draw is . I think starters are below the 200 amp limit on the 365 model .
Click to expand...

my fluke 30 doesn't do DC either :(

but it was free, so :)
Click to expand...
robably not going to fond starters below 200.
 
(quoted from post at 23:52:18 02/25/19)
(quoted from post at 00:16:34 02/26/19)
(quoted from post at 00:13:05 02/26/19)
(quoted from post at 12:34:15 02/24/19)
(quoted from post at 10:46:43 02/24/19)
Well the meter could be a problem ! Guess I'll have to get a good dc meter as well. If you guys know of a good one, let us know.
Click to expand...

If you are a Fluke man their 365 clamp meter ($200+) will measure AC/DC amperage up to 200A. With a resolution of .1A not going to be too useful for mA measurements.

TOH
Click to expand...

My primary job these days is a sewer lift repairman for the City of Hot Springs . I had never worked with 3 phase or diagnosed capacitors and such . 300 hp to 2 hp motors and controls . I have worked on plenty of gate operators from present to back when they were full of relays before the electronic control boards . The last year has been an exciting learning curve for me .

They furnish me a nice Fluke 324 which does everything I need at work , but you guessed it , no DC amp readings :( . I carry it with me , even home in case I get an emergency call in the middle of the night . I go above and beyond so I can usually ask for special tools and have pretty good luck getting them if it is during the budget high . I need to start thinking of a good reason I need a 365 other than I want to take it home to see what my starter amp draw is . I think starters are below the 200 amp limit on the 365 model .
Click to expand...

my fluke 30 doesn't do DC either :(

but it was free, so :)
Click to expand...
robably not going to fond starters below 200.
Click to expand...

Well I was feeling getty , but now , after looking up they are 300 - 500 range , I guess I'll go pout in the corner .
 
(quoted from post at 00:31:52 02/24/19) No resistor in there, just wound differently.
I have to question the amperage reading.
Doesn't seem like it would run with amperage that low.
I have not tried to read the amperage with my clamp on though.
Might just be an anomaly in what the meter reads.
Click to expand...

What kind of winding do they use to make these :roll:

Zero resistance coil

TOH
 
LMAO!

That is amazing.

I've seen coil ads from parts stores that say " has internal resistor" but this is the first one I've seen that claimed it has no internal resistance.

I'm not sure if the answer is as simple as the parts sellers not understanding basic electronics as much as it is a lack of comprehension of the English
language. They don't understand the difference between "resistance" and "resistor". Or if the manufactures instructions say "external resistor not required" it
means there is a resistor inside.

Lets see how long it takes for someone to use this ad as 'proof' that some coils do not have resistance.
75 Tips
 

I have a hi amp clamp that plugs into my volt meter its not as convenient as a all in one it works well tho... On some meters you set it to V DC and others mV a load is a load I would not worry about trying to average it out....

Leaving the key on is the killer...

Keep a eye out for a Vat-40 they go cheap I picked one up for $40 all that was wrong with it was the screw that retained the load knob had came loose and was binding it up when you turned it in to apply a load...

https://www.ebay.com/itm/BLUE-POINT-CLAMP-ON-AMP-PROBE-CA2-20-400A-CAPACITY-/163252692497
 
(quoted from post at 09:06:01 02/26/19) LMAO!

That is amazing.

I've seen coil ads from parts stores that say " has internal resistor" but this is the first one I've seen that claimed it has no internal resistance.

I'm not sure if the answer is as simple as the parts sellers not understanding basic electronics as much as it is a lack of comprehension of the English
language. They don't understand the difference between "resistance" and "resistor". Or if the manufactures instructions say "external resistor not required" it
means there is a resistor inside.

Lets see how long it takes for someone to use this ad as 'proof' that some coils do not have resistance.
75 Tips
Click to expand...

It undoubtedly has a liquid nitrogen filled case with a super conductor winding. Down side is you have to replenish the nitrogen on a regular basis ;-)

TOH
 
It undoubtedly has a liquid nitrogen filled case with a super conductor winding. Down side is you have to replenish the nitrogen on a regular basis ;-)

TOH
Click to expand...
:lol:

The fine print says, "If you can measure the resistance we have a job for you!"
 
(quoted from post at 09:35:00 02/26/19)
(quoted from post at 09:06:01 02/26/19) LMAO!

That is amazing.

I've seen coil ads from parts stores that say " has internal resistor" but this is the first one I've seen that claimed it has no internal resistance.

I'm not sure if the answer is as simple as the parts sellers not understanding basic electronics as much as it is a lack of comprehension of the English
language. They don't understand the difference between "resistance" and "resistor". Or if the manufactures instructions say "external resistor not required" it
means there is a resistor inside.

Lets see how long it takes for someone to use this ad as 'proof' that some coils do not have resistance.
75 Tips
Click to expand...

It undoubtedly has a liquid nitrogen filled case with a super conductor winding. Down side is you have to replenish the nitrogen on a regular basis ;-)

TOH
Click to expand...
.....and many don't know the difference in a resister (HRC followers) and resistor.
 
To close this our fellas. Had a chance today to use the timing jig. I purchased from Wild Bill Hokie (Thanks Hokie for that, your efficiency at order fulfillment is very impressive !). She is running much better now. Much less vibration.

To satisfy my curiosity on the amp draw of the coil wire. I wired a 10 amp ammeter between the pn 12250 resistor and the coil. Using the 2.9 (let's call it 3) ohm internally resistor (no resistor inside fellas, just winding/wire differences to achieve the 3 ohms vs. 2.5 ohms on the YT coil). The YT coil was 1/2 the price at $15 vs. the $30 Styner version. Anyway going to post a quick video of starting and running amps, and up/down rpm's. As Jesse has indicated, the avg. amps as measured by the meter of the running tractor is a long way from the coil killing 4 amps often mentioned here. It's pretty steady at about .7 amps, pretty dang low, but tractor runs fine with that. Sorry about the video movement, but was didn't have enough hands to hold it steady at operate choke, throttle, etc. So I'm still scratching my head as to why my former coil cracked, running these low amps. To be fair, I did not have a chance to test it's resistance before it went to coil heaven.
 
Think my first video was too long, let's try this short version.
[video play=false:6cb0cb5c31]https://forums.yesterdaystractors.com/videos/mvvideo32842.mov[/video:6cb0cb5c31]
 
(quoted from post at 21:27:19 03/13/19) Think my first video was too long, let's try this short version.
[video play=false:fbfcf374da]https://forums.yesterdaystractors.com/videos/mvvideo32842.mov[/video:fbfcf374da]
Click to expand...
ood, but".........too bad you didn't let the meter show the points closed, key on stalled current, too.
 
I tried, when I first got the dist back on, and cranked it for the first time, the meter did show about 3 amps, and fell below 1 when running. For the next couple times I shut it off, and left the key on it also showed about 3 amps. After those couple time, it never again showed 3 amps with key on, engine off. I thought it peculiar that after those initial couple situations, the engine never stopped with points closed. The engine starts so easily, I can't bump it to find the points closed position. Do you guys have an easy way to rotate crank to find it. Do not have a crank start handle.
 
(quoted from post at 08:43:46 03/14/19) I tried, when I first got the dist back on, and cranked it for the first time, the meter did show about 3 amps, and fell below 1 when running. For the next couple times I shut it off, and left the key on it also showed about 3 amps. After those couple time, it never again showed 3 amps with key on, engine off. I thought it peculiar that after those initial couple situations, the engine never stopped with points closed. The engine starts so easily, I can't bump it to find the points closed position. Do you guys have an easy way to rotate crank to find it. Do not have a crank start handle.
Click to expand...

Shut off the fuel and run it till it dies.

TOH
 
(quoted from post at 08:43:46 03/14/19) I tried, when I first got the dist back on, and cranked it for the first time, the meter did show about 3 amps, and fell below 1 when running. For the next couple times I shut it off, and left the key on it also showed about 3 amps. After those couple time, it never again showed 3 amps with key on, engine off. I thought it peculiar that after those initial couple situations, the engine never stopped with points closed. The engine starts so easily, I can't bump it to find the points closed position. Do you guys have an easy way to rotate crank to find it. Do not have a crank start handle.
Click to expand...
ou can't do the following with the key on or it might start and run over you: I make sure key OFF, then put in highest gear and rock the tractor by hands on rear tire while watching fan blades for small movement. Then try key on while looking for current. If good, fine, if not try again.
 
Thanks fellas two good ideas. Got the engine moved to closed points at start. This has been an interesting little experiment.
[video play=false:72b24123ae]https://forums.yesterdaystractors.com/videos/mvvideo32878.mov[/video:72b24123ae]
 
(quoted from post at 21:57:22 03/14/19) Thanks fellas two good ideas. Got the engine moved to closed points at start. This has been an interesting little experiment.
[video play=false:ddab2f63fb]https://forums.yesterdaystractors.com/videos/mvvideo32878.mov[/video:ddab2f63fb]
Click to expand...
ou should be happy, now that you have verified what I told you some time ago. Non-believers! So, now maybe enough more people have it brought to their attention that pretty much the ONLY way that they will melt their coil is, stalled and leaving the ignition key ON, not just while running, even with the incorrect ballast!!!!!!
 
Happy indeed. Like Ronald Reagan said, Trust but verify ! BTW that was a handy little trick to locate the closed point engine position. I was surprised at how easy it was to "bump it" in high gear by hand. Took all of about 2 minutes to find.
 
(quoted from post at 09:48:17 03/15/19) Happy indeed. Like Ronald Reagan said, Trust but verify ! BTW that was a handy little trick to locate the closed point engine position. I was surprised at how easy it was to "bump it" in high gear by hand. Took all of about 2 minutes to find.
Click to expand...
our numbers illustrate another good point. That is, that the 12250 ballast resistor (known to range from about 0.7 Ohms cold to about 1.7 Ohms glowing red hot) is essentially still "cold" at a resistance of about 0.7 to maybe as high as 1 Ohm when running at that average low current of approximately 0.8 to 1.0 amperes. Therefore the ballast does little to modulate running coil current and does the major function of reducing coil current when engine stalled/points closed/key on. But even that isn't enough to save a coil if left on too long, coil power (Watts) being about 1.8W running and 56.0 W stalled.
 
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