Based on the model number you provided I was able to locate the engine model number, CV15S-41567, and the coil you are referring to is called an ignition module. You are correct in thinking that the module is acts as points but it also acts like an automotive coil in that it creates a spark that is then sent to the spark plug. You should not be getting any voltage to the module on the black wire as that is a ground that makes the coil stop firing. I have provided a link on
How a magneto (module) works
to help you understand the operation of the module.
The module may need to be replaced.
First let’s try a few tests to see what is working and what is not.
Note: Be sure the parking brake is set.
Disconnect the black wire from the module.
Check for spark, you can do this by trying to start the engine.
If the engine starts you have a problem in the kill circuit.
If the engine does not start then the module has probably failed and should be replaced.
To check the kill circuit the first thing you must do is to test the black wire coming off the module for ground, while it is still disconnected from the module.
This can be done using a test light with the test light lead attached to the positive battery terminal.
Touch the test light tip to the black wire.
If the light does not come on there is no ground and the module must be replaced.
If the light comes on, the black wire is grounded and you should continue testing.
Unplug the ignition switch.
Set the switch to the RUN position.
Test for continuity between pins M and G.
If there is continuity the ignition switch has failed and must be replaced.
If there is no continuity the switch is ok. Turn the switch to the OFF position, reconnect it and go to the next step.
Turn the switch to the RUN position.
Go to the Operator Presence Relay #1 and check for ground at terminal 87A, (Located under the dash). Test the relay not the wire.
If there is ground the relay must be replaced.
If there is no ground here the relay is working, and proceed to the next step.
Replace the Ignition module.
The part number for the module is 12-584-04-S for $49.03 it comes with installation instructions.
The part number for the ignition switch is 140301 for $25.99
The part number for the Operator Presence Relay is 109748X for $15.99
The parts are available at
Sears Parts Direct
I have include below the wiring schematic for your tractor
If you do not feel confident repairing this problem yourself, then you can have it repaired at your home by a Sears technician. Here is a link for the website:
Sears Home Services
I hope this helps.