If your riding lawn mower keeps running in the off position, the key switch may have gone bad or the ground in the ignition coils may have a break in the wire. Mice can also chew these wires and cause this condition. All it takes is for them to chew through the gray or black wire and then the ignition coils will no longer receive a ground signal to kill the spark.
The ignition switch can do the same thing. You turn the key to the off position and if the switch is not working correctly, it will not allow the circuit to connect to ground and kill the spark. All you are doing is providing a path to ground and that is what makes the ignition coils ground out so to speak.
Check the ignition switch first by ohming across the off terminals to see if you have continuity to ground. If you do, the switch is good. If not, replace it.
Remove the blower cover to access the kill wires. Check the wire on top or bottom of the ignition coils and trace it back to see if it has any cuts or breaks in it. You can also ohm it out to ground and to the ignition switch to see if it is a good wire.
If you still cannot figure out why the riding lawn mower won’t shut off with the key, visit our Locations page for a lawn mower repair shop near you.