Pertronix/Hot-Spark/whathaveyou require that the coil have a primary resistance of 3.0 ohms or greater.

My confusion comes in here: If the coil is 1.5 ohms, and the resistor wire is 1.5 ohms...is the issue that the 'I' terminal on the solenoid provides 12 volts to the coil + during cranking (bypasses resistor)? <--Have discovered that is the mystery function of the second solenoid post, and Dura-Spark equipped vehicles don't utilize it because there were no points to burn.

Curious if there's a real world workaround for this, other than going to AutoZone and buying a $32 coil (Hot-Spark reports that an LU800 is 3 ohms...stock coil for many British cars of our era and available for pick up at my local AZ. I guess maybe Ford thought 1 coil over here, with resistor wire for 4 cyls, without for 8's was a way to cut costs. lol)

Electrical guru's, feel free to chime in. I don't care to melt $50 components due to my basic understanding of Ohm's law.

Thanks again, guys!

Ironically enough, I did some cross-checking, and a stock 71 Beetle coil is internally resistored at 3 Ohms. Found one at O'Reilly for $16.99.

Or I could be wrong. Parts stores all list 2, one states external resistor, one without. I got the one 'without'. *sheepish

I went that far back in my 'research'. They were still 6-volt systems then, yeah?

I have a Pertonix in my '64 Studebaker Daytona (350 Chevy powered).  I went a bit nuts-o like you are. I don't know if this solves your problem, but it might help explain:

1. A lot of people think because the Pertronix is an electronic device it sends 12V+ to the coil.  That is not true.  The Pertronix does exactly what the points do.  It makes and breaks the (-) negative side of the coil to ground - all be it electronically not mechanically like points.

2. With that in mind my Pertronix (the red wire) goes directly to 12V+ on the ignition switch.  A common mistake people make is to wire the red Pertronix power wire to the resistive side of the positive wiring.   This will allow the car to seemingly start (bypassed to 12V+), but as soon as the key returns to the "run" position it dies or runs awful because it is getting its power through the resistor.

3. It is the 12V+ that goes to the coil (and its subsequent current through a resistor) that determines the load (amperage).  I recall Pertronix had the math formula on their website to help simplify the process.   They stated that if the coil and resistor did not exceed a certain amperage you were OK.

4. Yes, most system typically have 12V+ to the coil at cranking and when the key goes to the "run" position it drops through the resistor.

5. If you have the lower end Pertronix (I do) you need to be careful not to have it powered without the car running. They say 30 seconds is the limit.  To facilitate testing with the key in the run position I have the red wire run through a bullet connector.  I disconnect as needed.

I am not familiar with the Hot Spark system.  But hopefully something I relayed will be helpful.   All the best and hope you get it sorted out.

Tom


 

Thinking the short term use of the 12V jumper off solenoid won't hurt. The problem comes from gradual overheating of the main switching transistor by using too much amp longer term. Eventually it fails the transistor.

I always try and take off an auxiliary terminal off the fuse box, that way I know it's a direct 12v. Now this time I found one in that reset switch on the fender, it put out 12.3 volts and seems to be working good, so far anyways..

Friend of mine made a safety switch out of the cigarette lighter, saved his car from being stolen once.