S1 Ducellier Coil Replacement

[My S1]

Sorry to ask you guys to rehash this old topic but reading through past posts I'm still a bit confused.  In my S1 I have a Ducillier 12V coil that puts out 1.8ohm.  I have a Lucas Sport (gold) that puts our 2.4ohm.  I believe but am too dumb to know for sure that the S1 uses an external balast.  In  the interest of keeping all systems as original as possible, what is the best replacement coil?  Someone mentioned that to use too low of an ohm output would reduce points life.  Does that translate into using the Lucas Sport (2.4 ohm) is OK?

[bjthomp]

The Ducel coil used in the S1 does not use an external ballast. I have been using a Bosch blue coil in my S1 for years and never had a problem with burned points. I'm no electrical guy, but as far as I know, a Lucas sport coil should work just fine.

[Richard48Y]

Um, the 1.8 ohm is primary resistance not coil output.
Output is going to be around 20K volts with either coil.
Primary resistance can be changed to suit using a ballast resistor.

[jbcollier]

The S1 does not have an external ballast resistor so it uses a "12v" coil with extra resistance built in. You need a coil with a primary resistance (measured from the + terminal to the - terminal) of 4 to 3 ohms.  4 ohms will give longer point life and a slightly lower potential-voltage spark output.  3 ohms will give a higher potential-voltage spark output but lower points life.  The gold Lucas Sport coil has 3 ohms primary resistance as does the Bosch Blue coil.  Both will work just fine.

I'm not sure how you are measuring your coils but you are getting false low readings.

[Richard48Y]

The One mod I am now making to all of my cars is to replace the points with another system.
It is an invisible upgrade.

[My S1]

I was measuring the coil simply with a multimeter set to om with the coil on the bench.  Sounds like I need to measure it running or at least hooked into the hot system?

At any rate, since I can not find an n.o.s. Ducillier I'll go with the Lucas Sprot.

Many Thanks to all of you for the advice.

[jbcollier]

Across the two small terminals?

What kind of multimeter?  Cheap and cheerful?

Do not use an ohm meter on a live circuit.

[My S1]

Across the two terminals.  Decent quality multimeter, fairly new.

[jbcollier]

I have four or five Flukes* and they all give consistently the same read outs.  I also have a few hardware store specials and they do not.  They are all off, some by quite a bit.

* I’m a retired mechanic.  I had three at work (automotive special, standard and one with a wireless head) and a couple at home.  Stopped working, dragged all my tools home and, voila.