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Error code reference

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

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

U-Line codesU-Line refrigerator codes

Left 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 L Temp Lo 12H+ means on a U-Line refrigerator

The L Temp Lo 12H+ error code on a U-Line refrigerator indicates that the left zone temperature has measured at least 10 degrees Fahrenheit below the user-configured set point for a continuous period exceeding 12 hours. This is a sustained overcooling condition, meaning the refrigeration system in the left zone is running too aggressively or the temperature sensing circuit is reporting falsely low readings. The 12-hour threshold ensures the alert reflects a genuine operational problem rather than a brief fluctuation.

The main control board governs relay operation, which in turn controls the compressor, evaporator fan, and defrost cycle timing. If a relay on the main control board is stuck in a closed position, the compressor or fan motor may run continuously without cycling off, driving temperatures well below the set point. This is why the first diagnostic step focuses on inspecting the main control board for proper relay operation, including listening for relay clicks during normal cycling and checking for signs of relay failure such as burnt contacts or heat damage.

Additional causes can include a faulty thermistor in the left zone reporting temperatures colder than actual conditions, a defective temperature control circuit, or a wiring fault sending incorrect signals to the control board. A stuck damper or a malfunctioning evaporator fan that runs beyond its intended duty cycle can also produce sustained overcooling. Systematic component testing, starting with the control board relays and moving to the thermistor and associated wiring, is the correct diagnostic approach.

Source: manufacturer service documentation.

Common causes of L Temp Lo 12H+

  1. 01

    Stuck or failed relay on main control board

    Part replacement

    A relay on the main control board that fails in the closed position can cause the compressor or evaporator fan to run continuously, overcooling the left zone without cycling off. Inspect the board for burnt relay contacts, heat discoloration, or listen for abnormal continuous operation of the compressor.

  2. 02

    Faulty left zone thermistor

    Part replacement

    A thermistor that has drifted out of calibration or failed can report a false temperature reading to the control board, causing the system to overcool in response to inaccurate data. Test the thermistor resistance values against the expected specification for the unit's operating temperature range.

  3. 03

    Wiring fault in temperature sensing circuit

    Wiring / connection

    Damaged, corroded, or shorted wiring between the left zone thermistor and the main control board can produce erroneous temperature signals that trigger sustained cooling. Inspect the wiring harness for pinching, corrosion at connectors, or breaks in the insulation.

  4. 04

    Stuck or improperly calibrated damper

    Part replacement

    If the airflow damper controlling the left zone is stuck open, excess cold air continuously flows into the compartment regardless of the set point. Visually inspect the damper for physical obstructions, ice buildup, or a failed actuator motor.

  5. 05

    Evaporator fan running beyond duty cycle

    Part replacement

    An evaporator fan motor that runs continuously without shutting off during its normal cycle can drive compartment temperatures far below the set point over time. Check whether the fan responds correctly to control board signals and stops when it should.

See the test procedure for each cause

Frequently asked questions about L Temp Lo 12H+

What does L Temp Lo 12H+ mean on a U-Line refrigerator?
This code means the left zone of your U-Line refrigerator has been running at least 10 degrees below your set temperature for more than 12 hours. It indicates a sustained overcooling condition rather than a brief cold spike. The refrigeration system in the left zone is not shutting off or cycling correctly. The first step in diagnosis is inspecting the main control board for proper relay operation.
How do I fix the L Temp Lo 12H+ error on my U-Line refrigerator?
Start by inspecting the main control board relays for signs of failure such as burnt contacts or continuous compressor operation without cycling. Next, test the left zone thermistor to confirm it is reading temperatures accurately and check the wiring harness for damage or corrosion. If the control board relay is stuck, the board will need to be replaced. A qualified technician should perform these checks if you are not comfortable working with appliance electrical components.
Will resetting my U-Line refrigerator clear the L Temp Lo 12H+ error?
A reset may temporarily clear the error code display, but it will not resolve the underlying problem causing the overcooling. If the faulty component, whether a relay, thermistor, or wiring issue, is not repaired, the left zone will continue to run too cold and the code will return. Always address the root cause before relying on a reset.
Is it safe to use my U-Line refrigerator while it shows the L Temp Lo 12H+ error?
Sustained temperatures well below the set point in the left zone can damage temperature-sensitive items such as beverages, produce, or certain medications. Foods that freeze unexpectedly may lose texture or quality. It is best to relocate sensitive contents and have the unit serviced promptly to prevent further damage to both food items and internal components.
How much does it cost to repair a U-Line refrigerator with the L Temp Lo 12H+ error?
Repair costs depend on which component has failed. A thermistor replacement is typically a lower-cost repair, generally in the range of $75 to $200 including parts and labor. Main control board replacement tends to be more expensive, often ranging from $200 to $500 or more depending on parts availability and labor rates in your area. Getting a diagnostic assessment from a qualified technician before purchasing parts is recommended.

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