How long will a set of "hot" points last...

[bm02tj]

More current more heat more heat more resistance

 

[RJRENTON]

RJ- this is what I meant by my post. I do see what you are saying, and agree,,, its just the term "variable". I read that as something one can vary. Electrical things vary with heat, so we could say that all electrical things/components are variable.

Yes....I, too understand your point, even using the standard IEC symbols and to a certain extent, the ISA (Instrument Society of America) symbols, having draw both using autoCAD programs, as a design engineer (BSEE).....but there are exceptions....such as MOVs (Metal Oxide Varistor), which responds to transient voltage spikes, VDR (Voltage Dependant Resistor) either as positive or negative dependant, or Thremistor (which changes its resistance in response to temperature), but when designing, a specific value of resistance is selected to achieve a specific result, subject to a tolerance (or variable) of the selected component's resistance.
BOB RENTON

 

[RemCharger]

Interesting and good information.. which leads me to a question. Does say an MSD resistor share the same qualities (if you will) as a factory Chrysler resistor ?

 

[RJRENTON]

I'm not familiar with the MSD circuitry and individual components other than what MSD means, which is: Multiple Spark Discharge, which produces a 200 volt pulse to the coil,which in turn, increases the spark energy to 40k volts. At lower RPM's, say less than 4000 RPM, the system provides several spark occurrences after that RPM, there is not enough time to charge/discharge the spark coil more than once per cylinder. The origional Mopar system was designed to simply replace the points as a maintenance issue. The control box simply switched the coil off, using a signal generated by the pickup coil in the distributor, to produce the spark then on to charge the coil for the next event. The ballast resistor simply limited the current to the coil and switching transistor to avoid overheating and subsequent damage. I believe the MSD system does not use a ballast resistor because the coil current is supplied via capacitor, internal to its control box. Not sure if that answers your questions.
BOB RENTON