Originally Posted by Bryan59EC
To check this correctly, you will need to disconnect the wiring to the + side of the coil.
If you leave the coil connected, that post will have voltage to it any time the engine is running or the key is on.
Disconnected from the coil-----you should be getting 12volts to the "I" terminal (or wire) while the starter is engaged----and nothing with the key off or key on and the starter not engaged
Yes the coil (+) from the solenoid needs to be disconnected but the voltage may (or may not depending on the starter load and battery size/condition) be less than 12 volts. The entire system voltage will drop due to the heavy load from the starter so the voltage may drop as low as 8 or so volts and still be correct. It will be correct if voltage is present while cranking but the voltage disappears when the switch is released to "run". Theoretically the voltage from the solenoid should be equal to or slightly greater than the output voltage of the resistor since it's purpose is to compensate for the drop in input voltage to the resistor that results from starter load, without this by-pass circuit the coil would not fire reliably due to low output voltage from the resistor resulting from low input due to cranking load.