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Error code reference

U-Line Refrigerator Error Code R Temp Lo 12H+

Right Zone temperature is -10° under set point for over 12 hours.

U-Line codesU-Line refrigerator codes

Right Zone temperature is -10° under set point for over 12 hours.

First step from the service manual

Inspect main control for proper relay operation.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What R Temp Lo 12H+ means on a U-Line refrigerator

The R Temp Lo 12H+ error code on a U-Line refrigerator indicates that the right zone temperature has been running 10 degrees Fahrenheit or more below the user-configured set point for a continuous period exceeding 12 hours. This is not a brief or transient temperature dip. The 12-hour duration threshold means the control board has detected a persistent, sustained overcooling condition in the right zone, which points to a system-level fault rather than a normal fluctuation during a door opening or defrost cycle.

The primary component to inspect first is the main control board, specifically the relay responsible for cycling the compressor or the cooling circuit for the right zone. A relay that is stuck in the closed position will keep the cooling system running continuously without cycling off, driving temperatures well below the set point. Relay failure on control boards is a known failure mode and can sometimes be identified by visual inspection for burn marks or by testing relay switching behavior with a multimeter.

Additional causes include a faulty thermistor in the right zone reporting incorrect temperature data to the control board, a malfunctioning damper assembly that is stuck open and allowing excessive cold air flow into the zone, or a wiring fault creating an erroneous sensor signal. Because the error requires 12 consecutive hours of overcooling to trigger, intermittent issues are less likely culprits. Systematic diagnosis starting at the control board relay, then moving to the temperature sensor and airflow components, is the recommended approach.

Source: manufacturer service documentation.

Common causes of R Temp Lo 12H+

  1. 01

    Stuck or Faulty Control Board Relay

    Part replacement

    A relay on the main control board that is stuck in the closed position will keep the cooling system running non-stop, causing the right zone to drop far below the set point. Inspect the relay for burn marks and test for proper switching behavior.

  2. 02

    Defective Right Zone Thermistor

    Part replacement

    A temperature sensor reporting a falsely high temperature will cause the control board to keep cooling even when the zone is already too cold. Testing the thermistor resistance against expected values for the current temperature will confirm or rule out this cause.

  3. 03

    Damper Assembly Stuck Open

    Part replacement

    If the damper controlling airflow into the right zone is stuck in the fully open position, cold air will flow continuously and overcool the compartment. Inspect the damper for physical obstructions, ice buildup, or mechanical failure.

  4. 04

    Wiring Fault or Short in Sensor Circuit

    Wiring / connection

    Damaged or shorted wiring between the thermistor and the control board can send incorrect signals that mimic a warm zone reading. Inspect the wiring harness for visible damage, pinching, or corrosion at connectors.

  5. 05

    Control Board Software or Calibration Error

    Part replacement

    In some cases the main control board may develop an internal logic fault causing it to misread zone temperature data. A power reset can be attempted, but a persistent error typically requires board replacement.

See the test procedure for each cause

Frequently asked questions about R Temp Lo 12H+

What does R Temp Lo 12H+ mean on a U-Line refrigerator?
This code means the right zone of your U-Line refrigerator has been running at least 10 degrees below the set temperature for more than 12 consecutive hours. The appliance monitors zone temperatures continuously and triggers this alert when sustained overcooling is detected. It indicates a component is likely keeping the cooling system running longer than it should. The first step in diagnosing the issue is inspecting the main control board for proper relay operation.
Can I fix the R Temp Lo 12H+ error myself?
Some steps, like inspecting the wiring harness for damage or checking the damper for obstructions or ice buildup, can be done by a knowledgeable DIYer. However, testing relay operation on the main control board and measuring thermistor resistance values requires a multimeter and comfort working with appliance electronics. If those components need replacement, many homeowners prefer to call a technician to avoid damaging the control board.
Will resetting the refrigerator clear the R Temp Lo 12H+ error?
A power reset may temporarily clear the error code, but if the underlying fault is still present, the code will return once the right zone temperature drops 10 or more degrees below the set point again for an extended period. Resetting is useful for ruling out a one-time control glitch, but a recurring error requires proper component diagnosis and repair rather than repeated resets.
Is the R Temp Lo 12H+ error a safety concern for my food?
Overcooling in a refrigerator zone can cause certain foods to freeze, leading to texture and quality loss in items like produce, beverages, and dairy. While an overly cold refrigerator is generally less of an immediate safety risk than an overly warm one, frozen or partially frozen food may be unusable. Addressing the error promptly will protect your stored items and prevent potential damage to the appliance from continuous compressor or cooling system operation.
How much does it cost to repair a U-Line refrigerator showing R Temp Lo 12H+?
Repair costs depend on which component has failed. A thermistor replacement is typically on the lower end of the cost range, often between 50 and 150 dollars including parts and labor. A main control board replacement is more expensive, generally ranging from 200 to 500 dollars or more depending on the specific model and local labor rates. Getting a diagnostic evaluation from a certified technician will provide a more accurate estimate for your specific situation.

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