The mounting plate is held in place by two or more screws. Remove the mounting plate.
The shutoff switch (labeled "A" below) is located near the shutoff arm (Labeled "B"). Remove the switch by removing the two screws that hold it in place. The switch is connected by three wires. Label the wire placement on the switch before disconnecting the wires. The wires are connected to the switch with slip-on connectors. Firmly pull the connectors off of the switch terminals (do not pull on the wire). You may need to use a pair of needle-nose pliers to remove the connectors. Inspect the connectors and the terminals for corrosion. If the connectors are corroded they should be replaced.
Replace the wires onto the new switch and fasten the switch in place. Make sure the shutoff arm is properly positioned to engage the armature (as shown above) before replacing the mounting plate.
Replace the outer cover, plug in the ice maker and refasten it to the freezer. Lower the shut off arm to turn the ice maker on.