ION-related IGN Comments & Coil Quest

[T Hergen]

An autotransformer (the auto has nothing to do with automotive) is one
that shares a common connection between the primary and secondary.  Using
an ohm meter, you'd find resistance bewteen any two terminals.

Since you mention the vortec, on mine, I tried measuring the resistance
between the high voltage terminal (to the distributor) and the case, but
didn't get any reading.  Assuming the coil is okay, this seems to indicate
that this coil doesn't use the metal frame as a ground.  Is this what
you'd expect?

Tom                                    

On Fri, 29 May 1998, Shannen Durphey wrote:

> Okay.  Here's what you got from the GM HEI coils. The IN CAP
> style have 5 wire terminals .  The BAT and C+ are connected
> to the primary positive side.  BAT is power in, C+ carries
> voltage to the module.  TACH and C- are connected to the
> primary negative side, and C- is switched by the module. 
> GND is connected to the iron frame of the coil and is the
> ground for the secondary.  Spark, of course, travels through
> the exposed metal portion which aligns with the carbon brush
> in the center of the cap.  
> 
> EXTERNAL style coils are very similar.  There are two
> connectors, each with two wires. In each connector one wire
> is pink and one is white.  Although they are not labeled,
> the  wires in the grey connector are BAT (large pink) and
> TACH(small, white, and often terminates close to the coil,
> taped back to the harness).  The wires in the black
> connector are C+(pink) and C-(white) and are part of a small
> harness which connects to the ignition module.  The design
> and function of these is similar to the above description. 
> There is no GND wire as the coil is bolted directly to the
> manifold.
> 
> Although they are probably difficult to find in the wrecking
> yards, the coils for the newer Vortec pickups and (if my
> memory is correct) LT1 type engines are electrically
> similar, but physically smaller.  The secondary terminal is
> somewhat recessed, and provides better coil wire retention. 
> Wire colors are different (and much smaller gauge, a sign of
> what?), but same function.
> 
> And now a brief question, found only by those who bother to
> read an entire post.  Will someone please give me a brief
> description of the difference between a transformer and an
> autotransformer?  (We could say that all transformers in
> cars are Auto transformers ; )
> 
> Shannen
>