Re: coil w/ internal resistor PLUS external resist

Posted by John T on July 29, 2006 at 08:57:16 from (66.244.90.5):

In Reply to: coil w/ internal resistor PLUS external resistor? posted by e-manhunt on July 29, 2006 at 08:04:26:

Manhunt, I agree with Jim, if its a true full 12 volt rated (some call internally ballasted) coil then there should NOT be another external Ballast Resistor, and if ones in place, the spark energy is less, although if so and the spark intensity is still sufficient for good starts n running, heck the points n coil should last a longggggggg time as the current draw n resulting heat is far less then their rating. If the engines in good shape and the carb n ignition are top shape there would be less problems but if shes low compression or an oil burner etc it may be harder to start in winter plus less power from using a 12 volt coil PLUS an external ballast.

I sort of question how you know or if it has an "Internal Resistor" Most all coils that are true full 12 volt rated (some call internally ballasted) coils are rated 12 volts cuz their primary winding resistance as measured between their lil + and - terminals, is somewhere around 2.5 to 3.5 ohms VERSUS a 6 volt coil which is more like 1.25 to under 2 ohms. The way the added resistance is usually achieved in a 12 volt coil IS USUALLY NOT via any discrete internal resistor BUT from either more turns of wire or wire of a higher resistance. The purpose n theory of how many ohms of ignition circuit primary total (coil + any ballast) resistance is to limit the amount of current the points are required to switch is around 4 amps maximum cuz otherwise they would burn up prematurely.

Soooooo take an ohmmeter on the Rx1 scale and measure the coils primary resistance between its lil + and - terminals, and if its around 3 ohms (means its a true 12 volt coil) YOU DONT NEED THE EXTERNAL BALLAST.

NOTE: True full 12 volt rated coils may be labeled something like "12 Volts" or "12 Volts NO Ballast required etc" HOWEVER if labeled "12 volts for use with external ballast" etc then its in reality a 6 volt coil AND THE EXTERNAL BALLST SHOULD BE USED or it will run too hot (you could barely hold your hand on it after running) plus the points burn up prematurely.

Read the coil label and/or use an ohmmeter to see if its a 6 or 12 volt coil, and if its a 12 REMOVE THE BALLAST BUT IF A 6 LEAVE IT IN PLACE

Hope this helps, best wishes n God Bless

PS I have reason to believe Delco may have made some coils that had a ring n groove at the top with a seperate compartment in which a discrete internal ballast resistor "may"?? have been housed HOWEVER most allllllll 12 full true 12 votl coils Im familair with acgheve the 3 ohms of primary resistance (making them a 12 volt coil) from higher resistance wire or else more wire period.

Post back any questions

John T

Replies:

• Re: coil w/ internal resistor PLUS external resist e-manhunt 07:13:54 07/30/06 (1)
  • Re: coil w/ internal resistor PLUS external resist Janicholson 10:00:45 07/30/06 (0)

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