I am in the process of converting my stock dist over to the Crane XR-i breakerless system.

In the instructions they cover the identification of the existing coil and whether it either:

a. uses resistance wire
b. uses an external ceramic ballast resistor
c. uses a coil with built in resistance

BALLAST RESISTANCE
1. All vehicles with OE breaker
points ignition are factory
equipped with ballast resistance.
This can be external resistance
in the form of a ceramic ballast
resistor or a resistance wire
between the ignition key and
COIL+ terminal. Most Chevrolet
vehicles have a resistance wire.
Ballast resistance can also be in
the form of internal resistance
within the coil. Coils with internal
resistance will measure 3 to 4
ohms from COIL- to COIL+ ter-minals.
2. If you are changing coils and
your vehicle has a ceramic bal-last
resistor or resistance wire,
do not use any additional ballast
resistor that may be provided
with the coil.
3. If your OE coil had internal resis-tance
and you are changing to a
new coil with lower resistance
(such as an aftermarket perfor-mance
coil), you must add a 1.2
to 1.9 ohm ballast resistor.

so first I check the voltage on the coil plus lead ... ignition on, engine not running; 12v.
Then I check it with the engine running; 12v (even at 3k RPM). So at this point it kinda rules out the resistance wire configuration. I then disconnect the wires from the coil and measure its resistance; 4.5 ohms. According to the Crane XR-i instructions, if the coil reads 4 ohms, then it's the internal resistance type (which would explain the absence of resistance wire).

BUT... here's the kicker. The coil plus terminal has two wires attached to it, one of these goes to the starter. If I remember correctly, this configuration was used only on resistance wire... and when the starter is engaged the extra plus terminal wire supplies a full 12v - not going through any resistance wire to give you a "hot" start.

SO... the way the coil is wired up, it would lead one to believe it uses the resistance wire... but the coil measures 4 ohms and the voltage on the coil stays a strong 12v with the engine running (I even disconnected the coils lead going to the starter to eliminate it being mis-wired).
AND the coil plus wire looks original, and goes into a factory wiring harness with no splices; and appears to not be resistance wire.

It would be helpful to determine what this 1973 L82
SHOULD'VE had from the factory. Was resistance "wire" used exclusively on the 1973's?





[Modified by Mike Mercury, 10:22 AM 5/26/2003]

 

problem solved; car had wrong ignition coil. It had the internal resistance variety, but shouldn't have.

read about the initial problems here:

http://forums.corvetteforum.com/zerothread?id=568369


ends up the car did indeed have the resistance wire.
The reason for no measured voltage-drop was that the bulk of the drop was occuring inside the incorrect coil due to it's built in resistor.


gee, I just quoted myself. Will I go blind? :)




[Modified by Mike Mercury, 12:51 PM 5/26/2003]