GE Monogram ZISB420DRB overcooling issues. This refrigerator has a temperature read out which displays actual temperature in addition to the preselected temperature. I have the Freezer set to 6F and the refrigerated section set to 46F, yet the refrigerated section gets down to 35F and the freezer section is at 4F. I tried a full reset and the unit has been cleaned out of its food but to no avail. I've replaced ALL of the thermisters except the one on the evap/section behind the metal shield in the freezer section (assuming there is more than on on/near the evap).
I've done tests on all 3 dampers (two for the express chill, 1 for the freezer to fresh section at top) and they all actuated properly. The EVAP fan works properly and there is nothing blocking the dampers that I can see.
I noticed that when the unit is warm like room temperature and then I turn it on, it is capable of getting its temperatures pretty close to their preset. However, after about a week or so, it eventually migrates to temperatures that are outside of its preset settings. This makes me think it's a thermister issue, perhaps with the evap thermister. I see no indication of frost buildup anywhere however, though I did not remove the rear freezer panel.
I technically could borrow a control board from another GE refrigerator which I believe uses an identical board but I'd like to do that option as last choice. I replaced this motherboard a few years ago because the condenser fan was spinning slowly, so I replaced the motherboard and the condenser fan motor and it spins normally since then.
Any other ideas? Could a defrost thermister cause this issue especially if the unit doesn't have any issues at all with frost build up on the evap coils?