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Error code reference

U-Line Ice Maker Error Code Temp Lo 12H+

Zone temperature is more than 10°F under set point for over 12 hours.

U-Line codesU-Line ice maker codes

Zone temperature is more than 10°F under set point for over 12 hours.

First step from the service manual

Check compressor, evaporator fan and related relays and DC outputs.

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

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What Temp Lo 12H+ means on a U-Line ice maker

The Temp Lo 12H+ error on a U-Line ice maker indicates that the zone temperature has remained more than 10°F below the configured set point for a continuous period exceeding 12 hours. This is not a momentary temperature fluctuation but a sustained condition, meaning the refrigeration system is either running excessively or the temperature sensing circuit is reporting an abnormally low reading. The 12-hour threshold is intentional, filtering out brief cold spikes and flagging only chronic overcooling events that point to a genuine system fault.

The primary suspects are the compressor, the evaporator fan, and the associated relays and DC control outputs that govern their operation. If the compressor is running continuously without cycling off, the zone will overcool steadily. A failed relay could hold the compressor in a constant-run state, preventing the normal off-cycle that would allow temperatures to recover toward the set point. Similarly, a malfunctioning DC output signal from the control board could be sending a constant run command even when the thermostat logic should be calling for a pause.

The evaporator fan is also part of the initial diagnostic focus because improper airflow distribution can contribute to uneven or excessive cooling within the zone. Technicians should verify that all relay contacts are opening and closing correctly, confirm DC output voltages from the control board are within spec during off-cycle periods, and check that the compressor is not running continuously. A faulty thermistor or temperature sensor reporting falsely low readings is another possibility that can mimic this condition without any actual overcooling occurring.

Source: manufacturer service documentation.

Common causes of Temp Lo 12H+

  1. 01

    Stuck or failed relay holding compressor on

    Part replacement

    A relay that fails in the closed position will keep the compressor running continuously, driving temperatures well below the set point. Inspect relay contacts for welding or carbon buildup and verify the relay is releasing during the normal off cycle.

  2. 02

    Control board DC output fault

    Part replacement

    A faulty DC output from the control board may send a continuous run signal to the compressor even when the temperature set point has been satisfied. Measure DC output voltages during the off cycle to confirm the board is properly interrupting the run command.

  3. 03

    Defective temperature sensor or thermistor

    Part replacement

    A thermistor that has drifted out of calibration or failed can report falsely low temperatures to the control board, triggering this error without genuine overcooling. Compare the sensor reading against an independent thermometer placed in the zone.

  4. 04

    Evaporator fan operating incorrectly

    Wiring / connection

    An evaporator fan running at incorrect speed or continuously when it should cycle off can push excessive cold air through the zone. Check fan motor operation, wiring connections, and the DC output controlling the fan.

  5. 05

    Ambient temperature or installation conditions

    Wiring / connection

    Extremely cold ambient conditions around the unit, such as installation in an unheated space during winter, can contribute to overcooling if the unit lacks adequate low-ambient protection. Verify the installation environment is within the specified operating temperature range.

See the test procedure for each cause

Frequently asked questions about Temp Lo 12H+

What does Temp Lo 12H+ mean on a U-Line ice_maker?
The Temp Lo 12H+ code means the zone temperature inside your U-Line ice maker has been more than 10 degrees Fahrenheit below the set point for over 12 hours. It indicates the cooling system is running too aggressively or the temperature sensor is reporting an incorrect reading. The 12-hour duration requirement means this is a persistent condition, not a brief fluctuation, and requires diagnostic attention.
How do I fix the Temp Lo 12H+ error on my U-Line ice maker?
Start by checking the compressor to see if it is running continuously without cycling off, then inspect the relays and DC control outputs from the board to confirm they are operating correctly. The evaporator fan and its associated wiring should also be examined. If a relay is stuck closed or the control board is outputting a constant run signal, those components will need to be repaired or replaced.
Will resetting my U-Line ice maker clear the Temp Lo 12H+ error?
A reset may temporarily clear the error code from the display, but if the underlying fault is still present the code will return once the unit has been running long enough to detect the same overcooling condition again. Resetting without fixing the root cause is not a permanent solution. The compressor, relays, fan, and control board outputs should be diagnosed before relying on a reset.
Is it safe to keep using my U-Line ice maker while the Temp Lo 12H+ error is active?
Continued operation while this fault is active is not recommended. A compressor running without cycling off can overheat and sustain internal damage over time. Additionally, if the overcooling condition is genuine rather than a sensor error, it may affect ice production quality. It is best to have the unit serviced promptly to prevent further damage.
How much does it cost to repair a U-Line ice maker showing Temp Lo 12H+?
Repair costs depend on which component has failed. A relay replacement is typically among the least expensive fixes, generally ranging from around $50 to $150 including parts and labor. Control board replacement or compressor work can push costs into the $200 to $600 range or higher depending on the specific model and labor rates in your area. A proper diagnosis is needed before accurate cost estimates can be given.

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