No good coil

[John Vardanian]

What are the general symptoms of a faulty coil? Thanks.

john

[Lowell]

How about measuring the resistance of the primary and secondary coils? The primary coils contact to the posts with nuts and should not have a lot of resistance. The secondary would be where the wire to the distributor plugs in and where the coil is grounded. This circuit should have a lot of resistance but not be open.

[DWR46]

John: in most coil failures, the car will intially run fine. However as heat develops in the coil, the engine will lose power until it dies by the side of the road. After a "cool off" period, the engine will start and run well again, then the cycle will repeat itself.

[John Vardanian]

Hi Dyke, that sounds like what I am experiencing. The car runs, but when I step on the throttle the power isn't there. The other thing is that when I compare resistance readings between the coils the readings are different.

Has anyone tried fitting a modern coil inside the original can? I am asking about this not because I'm cheap, but because I like the faded look of the Bakelite and want to keep it.

john

[John Vardanian]

Hi Dyke, how would the engine run if one of the distributor resistors was bad?

I am going thru things and noticed that with the ignition key on only one of the resistors gets hot. The other is quite cold. So, looking at your average ignition diagram on the internet, the resistor and the primary winding of the coil are in series, so if the resistor does get juice thru it neither does the primary coil, right?

john

[afwrench]

Hi John, I once cured a spotty running condition on my car by cleaning and securing all the connections on the resistors. Also a good idea to clean the coil towers themselves as arcing can occur there. Good luck ,Mike

[John Vardanian]

Thanks Mike, will do. The resistor for these coils is the "tootsie roll" style and they are hardwired internally.

john

[tim]

Hi Dyke, how would the engine run if one of the distributor resistors was bad?

I am going thru things and noticed that with the ignition key on only one of the resistors gets hot. The other is quite cold. So, looking at your average ignition diagram on the internet, the resistor and the primary winding of the coil are in series, so if the resistor does get juice thru it neither does the primary coil, right?

john

Greetings... If points are open, no current flow and no heat. It is entirely possible for the engine to have one disributor open and one closed and the closed one will heat up the resistor and the coil whilst the open one will remain cool.

Tim

[John Vardanian]

Hi Tim, you're absolutely right. Pardon my oversight.

Another question... with the points closed, shouldn't the voltage reading across the system be 6 volts, considering the effect of the ballast resistor, why do I get 12 volts?

john

[tim]

Greetings.. Where are you measuring. With points open and resistor and coil in the circut, I think you should get about 9V from the hot side of the points to ground. Remember, voltage is potential so you don't need current flow-except for the little bit through the meter.

Tim

[John Vardanian]

So, the problem wasn't the coils after all, it was one of the points in the right distributor. The edge of the leaf spring was touching the movable plate's lock-down screw and intermittently shorting the entire distributor. This, in spite of the electrical tape I had wrapped around the springs a couple of years ago when I serviced the distributors. Does anyone have a better idea? Thanks.

john

[afwrench]

Hi John, without seeing it I'm not sure about this suggestion. Sometimes the arm will ride up or down on the post.A small O ring stretched over the post or a plastic or fiber washer split and placed under the point arm should keep it above the screw. Could you use a screw that has a head that protrudes less? Good luck ,Mike

[DWR46]

John: Afwrench is correct. You should have fiber washers both above and below the movable point arm. This should raise the arm away from the screw head.

[John Vardanian]

Thanks Dyke and Mike. Yes, no doubt the fiber washers are in place. This last set of points I got, after putting them together I noticed one point doesn't center the complimenting point, so I added another layer of shimming to get them centered.

Mike, to your question, the problem came about during adjustment, from my screwdriver blade scraping against the electrical tape. The screws are the "panhead" style. If I shaved from the top or even from the diameter of the head the problem may well go away.

john