I have a Kitchen Aid ksra22fwhoo "architect series" fridge. The first problem was water leaking from underneath. Ifound the drain clogged and defrosted it. I have done this several times then added a piece of copper wire temporarily to heater,extending into drain to help keep it clear. This helped for a while and I thought the problem solved,but now the ref side is freezing. A thermometer shows around twenty degrees. This model has the diagnostics feature and I have run that several times everything always checks normally.The door between the boxes shows voltage and makes noise but I'm not sure how to tell if it's working. A hair dryer blown in the freezer side of the duct can be felt on fridge side so I know it's open.Also the refrigerator runs almost constantly but I'm inclined to think that it's not a low freon problem,cooling seems to be very good. I replaced the bi-metal defroster switch even though it checked ok just in case.All items in diagnostic check seem ok.
Great job on the defrost drain fix, it's exactly what we do. Check that the duct damper does close fully when the refer side temps are set to warmest. It could be freezing due to that damper not closing fully or at all. It should only be open to let cold air in until the temp is satisfied then closes again. The temp control in the refer may also be failed so it doesn't know the temp was reached. The bi-metal is only there for a safety device basically to kill power to the heat elements if the defrost cycle runs too long or the area gets too hot. I'd suspect the air damper is stuck open and contstantly letting cold air into the refer side.
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