After discussions with an appliance repairman, the problem was diagnosed as a thermostat issue in 20+-year-old fridge. I ordered a freezer defrost thermostat and main thermostat for this model per AppliancePartsPros.com and used the installation videos provided under the parts listing on the site. The videos were immensely helpful and informative. Of course, the repairs did take a bit longer than described, but I figured that would be the case (about 50% longer). The main thermostat part was not an exact replacement and the pins for the two control lines were placed differently. The new part had the pins labeled L and C while the original part’s pins were not labeled at all. A little online sleuthing revealed that the wiring color did provide the appropriate information: Orange = L, Black = C. Works like a champ again! I appreciate the service this site provides in finding the correct parts and then showing how to install them.