Re: Electrical question

Posted by Bob on July 25, 2006 at 23:03:03 from (64.21.249.40):

In Reply to: Re: Electrical question posted by Andy Martin on July 25, 2006 at 11:01:02:

Andy Martin,

If you can prove to me the existance of a modern "12-Volt" coil with an "additional internal resistor" that's "wound the same as a 6-Volt coil", I'll buy you a steak dinner!

We are talking here about a commonly available coil for a Kettering ignition system using breaker points.

The actual fact is that there is NO "discrete" internal resistor in 12-Volt coils. The extra resistance comes about through many extra winding turns in the primary of the "12-Volt" coil, vs. the primary of a "6-Volt" coil.

The internal "resistor" myth keeps popping up, but AFAIK, it has NO basis in fact.

As another poster stated, the reason a coil and external ballast resistor combination was used was to allow a "starting bypass", where full battery voltage was fed to the coil, bypassing the ballast resistor during cranking, to maintain a hotter spark while the available battery voltage is being reduced by the current demands of the starter.

Another topic not covered is "PTC" (positive temperature compensated) ballast resistors. Their resistance starts out low, and more or less doubles over a period of a minute or so after startup. This gives a HOT spark for cranking, then heating of the resistor causes it's resistance to rise, making life easier for the coil and breaker points.

As a general rule, systems using a starting bypass used a fixed-value ballast resistor.

Systems NOT using a starting bypass often used a "PTC" ballast resistor.

Replies:

• Re: Electrical question Andy Martin 05:40:42 07/26/06 (1)
  • Re: Electrical question Bob 08:54:35 07/26/06 (0)

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