6 Volt coil ohms check

[WPVT]

The coil on my 1954 Dodge 218 flathead gives me a secondary reading of 4800 ohms. I've heard various numbers quoted as to the acceptable resistance range, usually 6K-10K. This is the original Autolite CR 4001 with the integral bracket, so if I replace it I'll use a NOS Autolite to match. I don't intend to upgrade to better than original.

Is the 4800 ohm reading cause for concern or is it about where it should be ? 

[Bloo]

An ohm test is a terrible way to check a coil. An ohm test is a good way to check for a coil that is burned out completely, but that's about it. Coil testers that actually work are uncommon. I wish that weren't true, but it is. If the spark is good I wouldn't worry about it.

 

 

[TerryB]

I guess what your asking is if there are any shorted windings in your coil based on your measurements.  One thing to consider is the turns ratio of the primary winding to the secondary winding.  It’s based on transformer theory, if the primary winding has 10 turns and the secondary has 100 turns, the theoretical step up is 10x the voltage of the primary.  Using “typical” numbers may not mean much because the thickness or gauge of the wire is unknown as is the length of the wire in the secondary winding.  As Bloo said, the best way to measure is with a dedicated coil tester where the intensity of the spark produced is checked. I would be more concerned with the points and condenser to ensure they are in good condition and that the primary voltage to the coil is not lower than normal due to poor connections.  If the primary voltage is not within specification, the secondary will be lower than normal.

[edinmass]

I did a video on how to check a coil...........

 

Type in “Testing antique car coils” on YouTube, you will see my Herbrand  HT 660 coil tester. The coils would run the car and die, and restart in fifteen minutes. If you like, I will test your coil for free, just ship to me with a prepaid return label.

Edited November 13, 2020 by edinmass (see edit history)

[WPVT]

Thanks to all. The engine runs OK, and it sounds like the coil is probably good. It's not shorted out, gives a fat spark, and hasn't died when hot. Maybe I'll buy a NOS replacement, to keep on hand just in case.

It did seem to me that resistance testing a high voltage coil wasn't really effective unless it was shorted or open. 

And turn my attention elsewhere. 

 

PS I like your coil testing set-up Ed.