The ignition switch on your Mercury Sable is integrated into the ignition cylinder. When the switch fails, you may need to purchase a special switch from a Ford dealership if the switch used a wireless transponder (or is paired with a transponder inside the ignition key). Before replacing anything, however, you should troubleshoot the ignition switch.
Open the fuse panel cover under the steering wheel and locate the fuse for the ignition and starter. Use the fuse diagram on the underside of the fuse cover if you are having trouble locating the exact location of the ignition/starter fuse.
Pull the fuse out of the fuse box using the fuse pullers in the fuse panel.
Check the fuse. The metal strip inside the fuse should not be burned or damaged in any way. If it is broken, burned or damaged, replace the fuse with another fuse of the same amperage.
Put the ignition key into the ignition and turn the key to the "II" position. Crank the engine. You should hear a "click" when you first turn the ignition. If you do not, then the ignition switch has failed. If you hear a click but do not hear the engine cranking, then the problem may be with the starter and not the ignition switch.
