Our Maytag side-by-side Model MZD2766GEW has a problem with frost buildup on the bottom of the freezer side. The frost continues to build up until the refrigerator no longer cools. At this point, we usually manually defrost the unit, and the cycle starts again. Any ideas what could be wrong?

Thanks...

Sounds like the defrost timer switch bit the dust. This is a common part that fails on side by sides as well as top and bottom models. Check that out and more than likely you will need a new switch as there is no way to repair the switch.