Dan,
The ballast resistor, after getting heated up, serves as a voltage reducer
so the points don't burn up. Kinda like a rheostat.
Mike
----- Original Message -----
From: "Dan Neff" <neffster189@yahoo.com>
To: "Roadster Listgroup" <datsun-roadsters@autox.team.net>
Sent: Monday, July 16, 2001 11:14 PM
Subject: Ballast resistor Q
> I have a dumb question for y'all (hopefully dumb, and not: "oops, I
> discovered a P.O. fubar and didn't know it!")..
>
> What does the ballast resistor DO?
> I know this has been brought up before, but reading the wiring
> diagram, checking voltage at the coil, I'm not getting it. Would
> somebody mind trying again?
> My roadster service manual doesn't show the resistor in the wiring
> diagram! So, looking at a 510 diagram I have, I see a resistor between
> the ignition switch wire "IGN" and coil. Ignition sw "R" goes straight
> to coil. MY understanding was that when ignition was on START (that's
> "R"?) we went straight to coil, and when we're on RUN (that's "IGN"?),
> it goes thru the ballast resistor, such that the *resistor* reduces
> the voltage going to the coil (somebody gave me the idea it was 9V).
> OOKKKAAaaaayyyy..
> So I start my car, and voltmeter check the "+" on the coil -- it
> reads 12V! Huh? Well, whaddyer need a resistor for then? unless it's
> honked up wiring by a P.O.? I've driven it this way for 40,000 miles,
> so I'm guessing it's _right_, and I just don't understand why..
> I also don't get why there's no juice (0V at coil "+") when ignition
> is "ON", when car isn't running.
> Just out of curiosity, why does coil need a "-"? Why doesn't it just
> ground to chassis?
>
> Thanks,
> Dan Neff '69 2000
> Colorado Springs, CO
>
> p.s. if somebody gets into this stuff and yer on a roll, how 'bout
> explaining to me how the coil works? I understand how a 'coil'
> creates an electromagnetic field, but don't know my electronics well
> enough to understand how that automagically results in 30,000V from
> 12V! Let alone how a primary and secondary coil make this happen.
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