1. Removed and tested defrost heater, tests good. 2. Reinstalled defrost heater. 3. Removed and tested defrost over-temperature sensor, tests good. 4. Reinstalled over-temperature sensor using soldering iron, dielectric silicone grease, and heat-shrink tubing. 5. Removed the control printed circuit board and checked for blown fuse's, fuse's are all good. 6. Removed the defrost relay from the printed circuit board using soldering iron, bench tested the relay, it is good. 7. Soldered defrost relay back onto the circuit board, and reinstalled control board. 8. Removed and bench tested evaporator thermistor, the resistance is out of specification, ordered new thermister. 9. Installed new thermistor using soldering iron, dielectric silicone grease, and heat-shrink tubing. 10. Re-assembled refrigerator. 11. Installed temperature monitoring and recording instrumentation for 72 hour test. The defrost cycle is running correctly with a defrost termination temperature of around 90 deg-f. The defrost cycle ran twice while running the 72 hour test. 11. Removed test instrumentation and Put the unit back into service, The thermistor was the culprit. I bought the right part on the first shot, nice.
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