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Error code reference

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

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

U-Line codesU-Line ice maker codes

Right zone temperature is -10° 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 R Temp Lo 12H+ means on a U-Line ice maker

The R Temp Lo 12H+ error code on a U-Line ice maker indicates that the right zone temperature has fallen more than 10 degrees Fahrenheit below the configured set point and has remained in that condition for over 12 consecutive hours. This is a sustained low-temperature fault, meaning the unit is not simply responding to a brief temperature fluctuation but has been unable to maintain the target thermal range for an extended period. The 12-hour threshold is significant because it eliminates transient events like door openings or ambient temperature swings as the root cause, pointing instead to a mechanical or electrical failure within the refrigeration or control system.

The right zone's temperature is regulated by the compressor, the evaporator fan, and the associated relay and DC output circuitry that controls these components. If the compressor is running excessively or the evaporator fan is moving air too aggressively through the zone, temperatures can drop well below the set point. Conversely, if a relay is stuck closed or a DC output is sending a continuous signal to a cooling component, that component may run without cycling off, resulting in over-cooling. The control board monitors zone temperature through a thermistor, and when the reading stays 10 or more degrees under the target for 12 or more hours, this fault is logged.

Diagnostic work should begin by inspecting the compressor for proper cycling behavior, checking whether the evaporator fan runs continuously when it should cycle, and testing the relevant relays and DC output signals from the control board. A relay stuck in the energized position or a failed DC output driver can cause a cooling component to run non-stop. Wiring harness integrity and thermistor accuracy should also be confirmed to rule out a false reading driving the fault.

Source: manufacturer service documentation.

Common causes of R Temp Lo 12H+

  1. 01

    Relay stuck in closed position

    Part replacement

    A relay responsible for controlling the compressor or evaporator fan can fail in the closed or energized state, causing the component to run continuously without cycling off and driving temperatures too low. Inspect relays on the control board for signs of welding or burning and test continuity when the relay should be open.

  2. 02

    Faulty DC output from control board

    Part replacement

    If a DC output on the control board continuously sends voltage to the compressor or fan motor, those components will run non-stop. Use a multimeter to check whether the DC outputs are toggling correctly or remaining energized when the cooling demand should be satisfied.

  3. 03

    Evaporator fan running without interruption

    Wiring / connection

    An evaporator fan motor that does not stop when temperatures reach the set point will push chilled air through the right zone continuously, causing sustained over-cooling. Verify that the fan cycles off appropriately and that its wiring harness is not short-circuiting the control signal.

  4. 04

    Compressor not cycling off properly

    Part replacement

    A compressor that fails to shut down when the set point is reached will continue cooling the zone indefinitely. Check compressor run time and listen for continuous operation when the unit should be in an off cycle. The start relay and overload protector should also be evaluated.

  5. 05

    Inaccurate or failed thermistor in right zone

    Part replacement

    If the right zone thermistor is reading temperatures that are falsely low, the control board may believe the zone is warmer than it actually is and keep cooling components running. Compare the thermistor reading against an independent thermometer placed in the right zone to confirm accuracy.

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 ice_maker?
This code means the right zone temperature has been more than 10 degrees below the configured set point for over 12 continuous hours. It signals a sustained over-cooling condition rather than a brief temperature dip. The most likely causes involve the compressor, evaporator fan, or the relays and DC outputs that control those components. A technician should inspect those parts to identify what is preventing normal temperature cycling.
Can I fix the R Temp Lo 12H+ error on my U-Line ice maker myself?
Some preliminary checks, such as confirming the unit has adequate clearance for airflow and verifying no ice buildup is blocking the evaporator fan, can be done without special tools. However, testing relays, DC output signals, compressor cycling, and thermistor resistance requires a multimeter and working knowledge of refrigeration control systems. Most homeowners will need a qualified appliance technician to complete a proper diagnosis and repair.
Will resetting the unit clear the R Temp Lo 12H+ error?
A power reset may temporarily clear the fault code from the display, but it will not resolve the underlying mechanical or electrical issue causing the right zone to over-cool. If the root cause is not corrected, the fault condition will continue and the error will return after another 12-hour period of sustained low temperature. Resetting should be used only after a repair has been made, to confirm the fix was successful.
Is it safe to continue using my U-Line ice maker when the R Temp Lo 12H+ error is active?
The unit is running colder than intended in the right zone, which can affect ice quality and may stress refrigeration components over time. While the appliance is not typically a safety hazard to people in the way a gas appliance might be, running in a sustained fault condition can cause additional component wear. It is best to have the unit inspected and repaired promptly rather than continuing to operate it in a known fault state.
How much does it cost to repair a U-Line ice maker showing the R Temp Lo 12H+ error?
Repair costs vary depending on which component has failed. Replacing a relay or thermistor is generally less expensive, often in the range of $100 to $250 including labor, while a faulty control board or compressor repair can run $300 to $600 or more. A technician will need to diagnose the specific failed component before an accurate estimate can be provided.

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