Here are your parts
Parts for Maytag MFF2258VEW2 Refrigerator - AppliancePartsPros.comSee the attachment for the tech sheet.
Not sure why you feel the defrost goes through the ice maker.
I doubt this but stranger things have happened.
Perhaps the wiring layout in the tech sheet will help you trace this.
Below is my standard blurb about diagnosing defrost problems.
First remove the evaporator cover in the freezer so you can see the coils.
If they are heavily iced/frosted over then it is a defrost problem.
Do not let them de-ice.
If yes.
Manually force a defrost cycle, see the tech sheet. When the fans and compressor turn off, you are in defrost.
There is usually a hole in the cover to let you do this without taking anything apart.
Now check the defrost heater to see if it is on.
Be careful you do not want to burn your fingers.
If the heater is on then the control board needs replacing, re: it is never programming into a defrost cycle.
If not on.
Unplug the unit.
Remove the wire for one side of the heating element from the wiring and measure it for continuity, usually around 30 ohms or so.
If the heater is OK
Remove one wire to the defrost thermostat and measure it, should be 0 ohms when frozen. Note that it opens just above freezing so must be frozen to check it. Also inspect it, if it is bulged at all replace it even if it measures OK.
I could not find it in the parts but it should be clipped to the top of the evaporator coils.
If both the above are OK then odds are the defrost timer contacts are toast.
Best way to test this is a live test to see if you have 120 volts across the heater/defrost thermostat combo.