Most refrigerator icemakers perform the following functions.
Water Valve Switching - When certain conditions are met, a switch is closed in the icemaker head which allows AC current to flow to the icemaker 'fill' water valve, which is located in the bottom, rear area of refrigerator.
Temperature Monitoring - When the inside temperature of the freezer reaches 15 F the icemaker switches the water valve 'on' to allow water flow to fill the ice tray. If there is ice in the tray, 15F will not be reached since the ice temperature will keep the icemaker thermistor at roughly 32F and a harvest cycle may be triggered instead.
Heater - When the temperature holds at the 32F range for a period of time a harvest mode is triggered. A heater will activate and heat the bottom of the ice tray. The icemaker fingers will start to rotate to remove and drop ice cubes from the tray. At the end of the harvest cycle the water valve will turn 'on' for approximately 8 seconds to fill the tray.
You may recognize the hard-tray type of icemaker by the shape of the cube it puts out. The hard-tray Whirlpool and Kenmore icemakers produces half-moon shaped cubes. The flex-tray produces rounded rectangular cubes. The hard tray is finished in a dark gray or black color and has rotating fingers that eject the cubes from the unit. The flex-tray has a white plastic, flexible tray that inverts and twists to eject, much the same as a manual ice cube tray would work. The hard-tray is operated with a timer and is the most common refrigerator icemaker arrangement.
This most common icemaker, the hard-tray uses an integrated timer which is located in the icemaker head. Whether the compressor is running or not the icemaker motor has voltage applied to it. You cannot advance the icemaker like you can advance a defrost timer but on most models you can access the test points to put into harvest mode. You can also bypass the integrated thermistor to trick the icemaker into a harvest cycle and also test the water valve functionality.
To remove, unplug the refrigerator power cord. Obtain a shop light and extension cord to give yourself enough light to see what you are doing. Remove three hex head screws with a hex driver. Two are located along the top of the icemaker and one is on the bottom. The screws will secure the icemaker to the inside side wall of the refrigerator. When the icemaker is loosened, carefully disconnect the power connector and slide the icemaker carefully from the water tube.
When reinstalling the module be very careful to secure it to the side-wall with the water tube securely orientated so that water flows directly into the ice tray without spillage. Carefully inspect when finished. Re secure the power connector and reinstall the plastic cover if necessary.