v12 coil resistance questions?

[Beltfed]

Putting distributer back on car today.  Decided to measure resistance of coil.  To my surprise I got 4K (4000) ohm's.  I was expecting a much higher resistance.  I've always understood that the V12 coils would 'light you up').  Having measured a number of V8 coils of the cylinder types, they will generally measure around 10k or higher.  Being a former electronics person I know how coils works.  The more windings in the secondary for the flux lines to cut will give you a higher voltage output.  All the extra wire in the secondary coil give you more resistance.

So, what's with this lower value?

Is it possible my coils are partially shorted?

Thanks

[Ray500]

Coils can vary over time as there can be some shorted turns that still allow the coils to work.  Remember in these coils there are 2 different coils for the firing of the engine.  (Like 2-6 cylinder engines.  And when Skip Haney rebuilds them down in Florida he uses new Ford coil windings to make the coils fresh and higher voltage.  The old coils over time do deteriorate with the tar used to insulate the inside of the housing.  It would be better if you had him put fresh coils in your unit so you get higher voltage to run the engine.  Also new capacitors are very important to the firing of the ignition also.  They deteriorate over time also and need replacing.  

[19tom40]

The resistance seems low, but the true test of a coil is its output when hot.

 

 The best test is at idle when the engine is at operating temperature. The spark from a plug wire should jump about 1/2" when held near a good ground, like a head nut. The spark should be blue in color and make a sharp snapping sound.

 

 My coil tester is a SnapOm model that allows for heating the coil. The tester is basically a vibrator, to act as ignition points, and capacitor with a calibrated output that is adjustable to show spark intensity.

 

If your coils have not been rebuilt, you should do it before you put the car on the road. All of the original type coils will fail when they are used in a car. The question is when and the answer is usually when you are the farthest from home on a hot day.

 

Jake Fleming uses a different method from Skip Haney, of making the coils reliable. I have used his coils since the mid 1990's with the only failure occurring when I left the ignition switch on without running the car.

[Beltfed]

19tom40,  Do you have a model # for that coil tester?  Several years ago I built a spark plug tester, to go with my glass bead cleaner, out of a old door bell and a cylinder type coil.  I may have a go at a 'home brew' coil tester.  I already have a two channel oscilloscope but have never hooked it to for coil output, saturation, decay curve, and so on.  

Thanks

[Ray500]

14 hours ago, 19tom40 said:

The resistance seems low, but the true test of a coil is its output when hot.

 

 The best test is at idle when the engine is at operating temperature. The spark from a plug wire should jump about 1/2" when held near a good ground, like a head nut. The spark should be blue in color and make a sharp snapping sound.

 

 My coil tester is a SnapOm model that allows for heating the coil. The tester is basically a vibrator, to act as ignition points, and capacitor with a calibrated output that is adjustable to show spark intensity.

 

If your coils have not been rebuilt, you should do it before you put the car on the road. All of the original type coils will fail when they are used in a car. The question is when and the answer is usually when you are the farthest from home on a hot day.

 

Jake Fleming uses a different method from Skip Haney, of making the coils reliable. I have used his coils since the mid 1990's with the only failure occurring when I left the ignition switch on without running the car..

Leaving the ignition on without running the engine can cause the points to burn or weld together.  Jake does a good job, but he only cleans up the coils and replaces the tar resin with a silicon compound.  Over time the varnish on the copper windings is compromised and you can get shorted turns that can leave the coil putting out a lower voltage to the spark plugs.  This voltage can run some 15,000-20,000 volts to fire the plugs.  Low firing voltages can foul the plug with carbon.  I believe new copper windings that Skip installs are the best to renew the ignition.  The V12s need all the power they can get to run properly.  Jake does a great job calibrating the distributors on his scope setup.  

[19tom40]

Beltfed, here is a link to an add for the same model that I have.

 

http://www.2040-parts.com/snap-on-coil-tester-vintage-nice-1950-chevy-ford-buick-rat-rod-i8902/

[Ken/Alabama]

I would send the coil to Skip Haney . Then you'll know it's good and won't put you on the side of the road . If your coil is original and hasn't been rebuilt , it will fail. 

[Beltfed]

Y'all can come up with some of the neatest web sites.  I finally found the unit on '2040' but it was out of date, so no-go.  After figuring out how it works, it looks like an electric chair in a yellow box.  

[Waldren]

The resister on the firewall cuts the 6volt to 4 volt left side top bolt right side  bottom bolt.  Factory manual gives this for the wiring manual.  My 42 Continental runs great this way Skip rebuilt the coil.

[38ShortopConv.]

Beltfed, .. Coil Resistance..  Coil  on my 38 LZ. has  resistance of 4300 ohms on each secondary winding, the primary resistance is  0.8 ohms  each winding.  I  suspect  it  could have had new  innards.  I have run  coil for 20 years,  24000 miles. with a couple of distributor  resets, it has never missed a beat, runs strong. My spare get me home  coil  reads 4000 and 3700 ohms, is only  good for 90 miles. The ballast resistors add 0.8 ohms to the primary. I have always run   8 volt battery.  I did voltage and current tests with both 6 and 8 volt battery  and the readings were very similar, almost self ballasting. Ohms law suggests the higher the voltage the lower the current.  When the present 8 volt battery dies [ they last about 6 yrs.] are getting hard to get here, I'm changing to 12 volt. I have got  12 volt LZ. coil off Jerry Richman, it measures 4600 ohms!!  each secondary, 0.8 ohms primary, new ballast  resistors  0.8 ohms  same as old resistors.  I think a lot of the spark  ' Flux ' intensity relies on the condenser  capacity!!  38mf. ?  Could this make the condenser a  ' Flux Capacitor."  Back to the future. Things to ponder over. Roy.

Edited January 7, 2017 by 38ShortopConv.
just thought of it. (see edit history)