On 4 Nov 1994, Rob Reilly wrote:
> Converting 12-V Positive Ground (Earth) Cars to Negative Ground
> Version 1.0 (draft)
>
> 2. What reasons are there to convert?
> A. Permit use of a modern 12v neg ground radio
> B. Ignition coil provides a better spark
> C. Use of an alternator
"B" is incorrect. If the low tension wires are connected correctly at
the coil, the spark will be just as good either way.
> 3. Arguments against?
> Positive ground = less corrosion at the battery terminals (this is just
> something I've heard, can anyone confirm whether it is true?)
Not true.
> 4. Do the following components (if the car has them) need to have the
> polarity switched?
>
> coil - no, leave terminal CB or "-" to the distributor, because in every coil
> the primary winding is from SW to CB or from + to -, the secondary winding is
> from CB or - to the center tower. By connecting a coil in this fashion, the
> CENTER electrode of the spark plug will assume NEGATIVE polarity. The center
> electrode of the plug is always hotter than the side electrode. Since it
> takes less voltage to cause electrons to move from a hot to a cold surface,
> current flow must be from the hot center to the cooler side electrode. If the
> coil is connected wrong 20-40% more voltage will be required to fire the
> plugs.
It isn't that simple, because the winding scheme depends on whether the
coil was intended for use with positive or negative ground.. If the coil
is marked "CB" and SW" and was intended for use with positive ground, then
you need to reverse the connections so that CB connercts to the ignition
switch and SW connects to the points. If the coil is marked "CB" and "SW"
and was intended for use with negative ground, then connect CB to the
points and SW to the switch. If the coil is marked "-" and "+", then
connect - to the points and + to the switch.
-----------------------------------------------------------------------
Chip Old 1948 M.G. TC TC6710 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO (daily transportation)
feold@umd5.umd.edu
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