Food is starting to thaw and temperature around 40. Here is what I have done:
1). Diagnostics came back with no fault code.
2). Removed evaporator cover and top coils totally iced up restricting air flow
3). Removed all ice build up and allowed to come to room temp. Cleaned drip pan of water buildup.
4). Reassembled and turned on to default temp condition. Compressor ran approximately 1 minute and then shut down.
5). Diagnostics still no fault code.
6). Installed new control board/unit. Diagnostics showed evaporator thermistor code. Measured resistance and is not open. (not sure what value should be at room temp)
7). Checked wiring from control unit to thermistor and appears not open. Ran diagnostics again and now no fault code.
8). Put in diagnostic mode again and turned on compressor. (waiting to see if it gets cold)

Not sure where to go from here. If unit freezes with compressor only in diagnostic mode then would suspect problem with defrost circuit. Looking for suggestions. Electronics technician but not good with refrigeration.

Unit only 2 years almost to date.

ram5thwheel

Solved the problem but not with any help or should I say, responses to my problem.

Evaporator thermistor resistance measured approximately 150 ohms when measured out of circuit. After checking with an appliance store tech and having them look up on their engineering site the typical resistance of the replacement part (2,700 +/- 3% ohms) I ordered the replacement part and system is back up and running without issues.

Question why the diagnostics did not repeatedly show a diagnostic code with a definite defective part. In any case, closed!