KitchenAid Refrigerator KFIS29PBMS00 RC ok FC not cooling

[hong]

Model Number

KFIS29PBMS00

Brand

KitchenAid

Age

6-10 years

KitchenAid Refrigerator KFIS29PBMS00 RC works ok. Believe it's a dual evaporator.
In diagnostics, FC thermistor passes the test, FC fan works ok and when compressor is on the temperature at the FC fan air vent is slightly lower than ambient.
However, in normal operation, FC fan does not come on.
I think there may be two possibilities,
1. False thermistor diagnostics. The thermistor is in fact faulty. What is the part number?
2. Control board is bad.
Which one is more likely? Should I start with cutting off the thermistor from the wires and take a measure?

 

[Jake]

FC stands for Freezer Compartment, for others following your thread.

Did you remove the back panel inside the freezer and look at the frost pattern of the freezer evaporator coil?

Normal would be a thin layer of frost on ALL the coils from TOP to BOTTOM.

Look at the very bottom photo below where it says NORMAL FROST PATTERN.

 

[hong]

Hi Jake, yes, FC means freezer compartment. I haven't opened the back panel inside the freezer yet. I turned off the fridge for a few days and the temperature in FC has been over 60F.
The thing now is the FC fan does not come on even though in diagnostic it works ok. Yet the FC thermistor passes diagnostics.

 

[hong]

Now symptom changed. Freezer fan turns on, but freezer compartment temperature is close to 60F. The refrigerator compartment continues working fine. Maybe the problem is the thermistor in the freezer compartment?
What's the part number of the thermistor? Are the thermistors in freezer and refrigerator compartments the same?

 

[Jake]

but freezer compartment temperature is close to 60F.

That would usually be a sealed system issue, that's why its good to remove the back panel inside the freezer and look at the frost pattern of your evaporator coil.

Normal would be a thin layer of frost on ALL the coils from TOP to BOTTOM.

Look at the very bottom photo below where it says NORMAL FROST PATTERN.