Model #MFI2067AES, this bottom mount french door refrigerator which goes by the Ice2O moniker had decided to act like a freezer and would freeze everything in the upper fresh food section. The customer noticed things like vegetables would have ice on them and the milk would begin to freeze. Continuous adjustments were made to the fresh food and freezer temperatures, but nothing seemed to make any difference.



These popular french door refrigerators operate like most other frost free units, in that the cooling takes place within the freezer section, and this cool air is circulated by a fan into and around the fresh food section. To help control the temperature and allow the two sections to maintain a different temperature, a refrigerator part called an air diffuser or damper is used to control the flow of cooled air. This acts like a doorway letting in cold air from the freezer section until the temperature in the fresh food section is achieved. Then the door will close allowing the freezer to continue to cool to a lower temperature independent of the refrigerator section.

This process of moving cool air between sections works very well, and requires only a few parts to keep things working properly. Many refrigerators use a simple mechanical air damper and cold control to maintain temperatures which is effective, but can allow for wide temperature swings because of the passive nature of a mechanical damper. Most, let's say higher end products, use an electromechanical damper that is controlled by it's own cold control, or by the refrigerators main board to very accurately control the temperature within the fresh food section. These units are also going away from using mechanical cold controls, and are now using thermistors to monitor temperature.

Thermistors are semiconductor devices that change in resistance based on the temperature they are exposed to. The ones used in most refrigerators are called NTC for negative temperature coefficient, meaning their resistance goes up, as the temperature goes down. They are very accurate in their readings, and allow for specific temperatures to be maintained within both the freezer and fresh food sections.

On the refrigerator I was working on, I could quickly tell the fresh food section was much colder than it should be, and by placing my hand up near the air inlet, could feel the cold air continue to enter. By placing the unit into a diagnostic mode and scrolling to the temperature readings, I could see the freezer, ice box, and ambient temperatures seemed to be correct, while the fresh food thermistor said it was 44 degrees inside. This would explain why the damper was open and the electronics were trying to get it back to the preferred temperature. But before I start ordering parts, it's time to get out the multimeter and see if the thermistor is the problem, or maybe the control board is the issue.

To do this, I simply consulted the wiring diagram for the unit and isolated the connector and wires that lead to the fresh food thermistor and took a resistance reading. As outlined in the tech sheet, the thermistors should read around 29K ohms at 37 degrees, but I was getting a reading of only 12.5K ohms, which the control board would interpret as a much warmer reading. This would explain why the control board had the fan running and the damper wide open trying to cool down the fresh food section.

Looking like a thermistor problem, I removed the lamp assembly in the top of the fresh food section where the thermistor resides, and with power removed from the unit, replaced the thermister using the supplied crimp connectors. Then to ensure moisture doesn't cause a problem in the future, used some Whirlpool adhesive to seal the opening to the connectors. After putting everything back together, I put the unit back into diagnostics, and this time, the thermistor was reading properly.

By the way, this is one of those failures that can have multiple causes and not all require replacing a part. Due to the location of the thermistor in the top of the unit, the actual temperature will often times be accurate, but if measured in the crisper or deli drawers, is found to be much colder. This can be corrected by selecting a higher temperature for the fresh food section to help even things out. Also, if by chance you have an Ice2O version like the one in this post and do not have it connected to a water source, make sure the ice maker is turned off. With the ice maker on, and not making ice, more cold air will be drawn into the fresh food section because the electronic control board is trying to make ice. Simply turn off the ice maker to set things right. And finally, pay attention to how you load your food items on the shelves. In particular, avoid placing large items close to the air inlet which will disrupt the air flow, resulting in more cold air being pushed down the back of the unit instead of evenly dispersing throughout the cavity. If this all looks good, then it may be time to look a bit deeper into the problem.

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