Viking Freezer - Thermistor Alarm Issue

[MattyD7]

Viking model DFFB304L standalone 15.9 cuft freezer.

Issue: Freezer trips the Thermistor alarm but also continues to run constantly. Thermistor seems to work correctly.

Usually immediately upon plugging in, freezer beeps 5 times and the temp scale flashes left-to-right indicating thermistor alarm. If I clear the alarm, it usually trips almost immediately again. Sometimes it will not trip for a few minutes to few hours, but this is less common. Service Manual indicates that thermistor alarm is triggered by an OPEN circuit at thermistor, which also should cause the compressor and fan to shut off. However it continues to run constantly with alarm tripped. Pulled thermistor while power on to simulate OPEN circuit, and it shuts off compressor/fan immediately.

Tested thermistor resistance at different temperatures and compared to book values and it is very close at all temps ranges. Tested both with thermistor removed from freezer and while installed using digital multimeter. 

Entered the diagnostic mode and display shows what it reads the thermistor temperature. Using the binary code from service manual, confirmed that it is very close to the actual temp (tested with IR gun), so seems that the computer is reading the thermistor, and reading it accurately. Also as I keep door open, the value changes so it seems to be reading constantly and updating. However alarm is still triggered during before, during, after this diagnostic test.

Question: Service Manual indicated the only reason for thermistor alarm is if it detects OPEN circuit, but freezer runs constantly, and testing with multimeter and diagnostic mode seem to indicate the thermistor is operating correctly and that the computer is reading the value correctly and consistently. Is there any other failure mode that someone is aware of that would trip the thermistor alarm? Furthermore, any ideas what the issue could be, and how I could diagnose? If it is a problem with one of the PCBs, I have the wiring and PCB diagrams, what should I test to look for an error on the computer?

[lvasquez11]

You can start withThermistorPart number: WPW10331672 ( unless u would like to pay Vikings price). Is it holding proper temps? You state that it runs constantly?