Before testing the shutoff switch, unplug the
refrigerator to avoid an electrical shock hazard.
There are
two types of ice makers, those in which all of the parts can be
individually replaced and those in which some of the parts are
clustered together into a control module. To determine which model
you have remove the outer face plate. If there is knob, pull it
off first, then pry off the face plate with a small screwdriver.
Modular
units have holes in the module's face plate for test probes. If
you see several holes, each marked with a letter, it is a modular
unit. Component units (like the one shown below) usually have
exposed gears and don't have holes for test probes.
Modular units
do not use a separate shutoff switch. Instead follow this link
to view instructions for checking the shutoff
arm.
Before testing the shutoff switch, unplug the
refrigerator to avoid an electrical shock hazard. 
