Don't get stuck with a job half done due to a faulty ignition coil. A bad ignition coil on a Ford 9N tractor will cause starting problems. The ignition coil, located under the hood of the tractor, increases the voltage of the battery to a high enough level to start the 9N's engine. There are primary and secondary wire coils in the interior of the ignition coil housing . Each wire needs to be at a specific resistance to provide the voltage needed by the tractor.
Open the hood of the Ford 9N tractor, then disconnect both battery terminals.
Remove all wires connecting to the ignition coil and remove the coil from its harness.
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Turn on the digital multimeter and switch its measurement dial to the ohm setting. An ohm is a unit of measurement for electrical resistance. On some multimeters, it is designated by the capital Greek letter omega.
Connect the black (negative) probe of the multimeter to the outer, negative post of the ignition coil. Connect the red (positive) probe of the multimeter to the outer, positive post of the ignition coil. The multimeter reads the resistance of the primary coil. If the reading does not fall in the range given by the Ford 9N service manual for your model year, the ignition coil should be replaced.
Disconnect the black probe of the multimeter and hook it up to the central, negative post of the ignition coil. The multimeter now reads the resistance of the secondary coil. An ohm reading not in the range specified in the Ford 9N service manual for the secondary coil means the ignition coil is bad.