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Error code reference

U-Line Ice Maker Error Code L Zone T Open

Left zone thermistor circuit is open.

U-Line codesU-Line ice maker codes

Left zone thermistor circuit is open.

First step from the service manual

Check connection. Replace if necessary.

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

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What L Zone T Open means on a U-Line ice maker

The L Zone T Open error on a U-Line ice maker indicates that the left zone thermistor circuit has an open condition. A thermistor is a temperature-sensing resistor whose resistance changes predictably with temperature. An open circuit in this context means the control board is receiving no signal from the left zone thermistor, either because the circuit is physically broken or the thermistor itself has failed. The control board interprets an open circuit as a fault condition because it cannot make temperature-based decisions for the left zone without a valid sensor reading.

The most common cause of this fault is a loose, corroded, or disconnected wiring harness connector at either the thermistor end or the control board end. Connectors in refrigeration environments are exposed to moisture and temperature cycling, both of which can degrade electrical contacts over time. A broken wire within the harness is also possible, particularly at points where the harness bends or is routed near moving components.

If the wiring and connectors check out visually and electrically, the thermistor itself may have failed internally. A failed thermistor will show infinite resistance when measured with a multimeter, confirming the open circuit condition. Replacing the left zone thermistor is the corrective action when the sensor itself is the source of the fault. Always inspect the full wiring path from the sensor to the board before condemning the thermistor.

Source: manufacturer service documentation.

Common causes of L Zone T Open

  1. 01

    Loose or disconnected wiring connector

    Wiring / connection

    The connector linking the left zone thermistor to the wiring harness may have come loose or partially disconnected. Inspect both the thermistor-side and board-side connectors and reseat any that are not fully engaged.

  2. 02

    Corroded or damaged connector terminals

    Part replacement

    Moisture exposure in ice maker environments can cause terminal corrosion that breaks electrical continuity. Look for green or white oxidation on the connector pins and clean or replace the connector as needed.

  3. 03

    Broken wire in the harness

    Part replacement

    A wire in the thermistor circuit may have broken internally, especially at a bend point or near a vibrating component. Use a multimeter to check continuity along the full wire run from thermistor to control board.

  4. 04

    Failed left zone thermistor

    Part replacement

    The thermistor itself may have failed open, meaning it no longer conducts electricity. Measuring infinite resistance across the thermistor terminals with a multimeter confirms this failure and the sensor must be replaced.

  5. 05

    Faulty control board

    Part replacement

    If the wiring and thermistor both test correctly, the control board input circuit for the left zone sensor may have failed. This is the least common cause and should only be considered after all other components are ruled out.

See the test procedure for each cause

Frequently asked questions about L Zone T Open

What does L Zone T Open mean on a U-Line ice_maker?
L Zone T Open means the control board has detected an open circuit in the left zone thermistor circuit. The thermistor is the temperature sensor responsible for monitoring the left zone of the ice maker. An open circuit means the board is receiving no signal from that sensor, which triggers the fault. The issue is typically a disconnected wire, corroded connector, or failed thermistor.
How do I fix the L Zone T Open error on my U-Line ice maker?
Start by checking all wiring connectors in the left zone thermistor circuit and reseating any that appear loose. Inspect the connector terminals for corrosion or damage. If the connectors look good, use a multimeter to test the thermistor for continuity. A reading of infinite resistance confirms the thermistor has failed and needs to be replaced.
Is it safe to continue using my U-Line ice maker when this error is displayed?
Operating the unit with an active L Zone T Open error is not recommended. Without a functioning temperature sensor in the left zone, the control board cannot properly regulate temperatures in that area. Continued operation could result in inadequate ice production, food safety concerns if the unit is a combo appliance, or potential compressor damage from unmonitored conditions.
How much does it cost to fix the L Zone T Open error on a U-Line ice maker?
If the fix is simply reseating a connector, there may be no parts cost at all, only the cost of a service call ranging from roughly 75 to 150 dollars. Replacing a thermistor sensor typically costs between 20 and 60 dollars for the part, plus labor. If the control board requires replacement, costs can rise to a range of 150 to 400 dollars or more depending on the specific model.
Will resetting my U-Line ice maker clear the L Zone T Open error?
A reset may temporarily clear the error code from the display, but if the underlying wiring or thermistor fault is still present, the error will return once the control board re-runs its diagnostics. A reset is not a repair. The physical cause of the open circuit must be identified and corrected to permanently resolve the fault.

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