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Error code reference

Amana Refrigerator Error Code Open Thermistor

The freezer or refrigerator thermistor circuit is open, wiring to thermistors is open, or the L.V

Amana codesAmana refrigerator codes

The freezer or refrigerator thermistor circuit is open, wiring to thermistors is open, or the L.V. board has failed; freezer or refrigerator indicator lights 4 through 7 will sequence until ALARM OFF is pressed.

First step from the service manual

Check thermistor resistance and wiring; press ALARM OFF to silence alarm.

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

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What Open Thermistor means on a Amana refrigerator

The Open Thermistor error on an Amana refrigerator indicates that the control system has detected an open circuit in the thermistor loop for either the freezer compartment, the refrigerator compartment, or both. Thermistors are negative temperature coefficient (NTC) sensors that change resistance in response to temperature. When functioning correctly, they provide the low-voltage (L.V.) control board with a continuous resistance reading that the board uses to regulate compressor cycles and maintain target temperatures. An open circuit means that signal has been interrupted entirely, and the board can no longer read temperature data from that sensor.

The fault can originate in one of three locations: the thermistor itself, the wiring harness connecting the thermistor to the L.V. board, or the L.V. board's thermistor input circuit. A failed thermistor will typically measure infinite or out-of-range resistance when tested with a multimeter. Wiring faults, including broken conductors, corroded connectors, or pinched harnesses, can also produce an open-circuit reading even when the sensor is mechanically intact. If both the thermistor and wiring check out correctly, the L.V. board itself may have a failed input stage.

When this error is active, the refrigerator or freezer indicator lights 4 through 7 will sequence in a repeating pattern as a visual alarm. Pressing the ALARM OFF button silences the alarm indicator, but this does not resolve the underlying fault. Diagnosis should begin with a resistance check of the thermistor at the sensor connector and a visual inspection of the wiring harness for damage or disconnection.

Source: manufacturer service documentation.

Common causes of Open Thermistor

  1. 01

    Failed thermistor

    Part replacement

    The thermistor sensor itself has failed internally, producing an open circuit. Testing the thermistor with a multimeter at its connector will show infinite or no resistance rather than the expected value for the ambient temperature.

  2. 02

    Open or broken wiring harness

    Wiring / connection

    The wiring between the thermistor and the L.V. board may have a broken conductor, a loose connector, or a pinched section, interrupting the circuit. A careful visual inspection of the harness routing and a continuity test of each wire will identify this fault.

  3. 03

    Corroded or disconnected connector

    Wiring / connection

    Moisture inside the refrigerator cabinet can cause the thermistor connector pins to corrode, increasing resistance to the point of an effective open circuit. Inspect the connector for green or white oxidation and ensure it is fully seated.

  4. 04

    Failed L.V. control board

    Part replacement

    If the thermistor and all wiring test correctly, the low-voltage control board's thermistor input circuit may have failed. This is diagnosed by process of elimination after ruling out the sensor and harness.

See the test procedure for each cause

Frequently asked questions about Open Thermistor

What does Open Thermistor mean on a Amana refrigerator?
It means the control board has detected a break in the circuit connecting one of the temperature sensors (thermistors) in the freezer or refrigerator compartment. Without a functioning thermistor signal, the board cannot monitor or regulate the internal temperature properly. The indicator lights 4 through 7 will sequence as a visual alert until ALARM OFF is pressed. The fault can be caused by a bad thermistor, damaged wiring, or a failed L.V. control board.
How do I fix the Open Thermistor error on my Amana refrigerator?
Start by pressing ALARM OFF to silence the indicator lights, then check the thermistor resistance with a multimeter at the sensor connector. If resistance reads infinite or out of range, the thermistor needs replacement. If the sensor tests correctly, inspect the wiring harness between the thermistor and the L.V. board for breaks, loose connections, or corrosion and repair as needed. If both the sensor and wiring are intact, the L.V. control board may require replacement.
Will resetting my Amana refrigerator clear the Open Thermistor error?
Pressing ALARM OFF will silence the visual alarm (the sequencing indicator lights), but it will not clear the underlying fault. The error will return as long as the thermistor circuit remains open. The root cause, whether a failed sensor, a wiring fault, or a board issue, must be repaired before the error will stop recurring.
Is it safe to keep using my Amana refrigerator when the Open Thermistor error is active?
Continued use carries some risk, because the control board cannot accurately monitor internal temperatures without a working thermistor. The refrigerator may not cool properly, which could allow food to warm to unsafe temperatures. It is advisable to check food temperatures with a standalone thermometer and address the repair as soon as possible rather than relying on the appliance to maintain safe conditions.
How much does it cost to repair an Open Thermistor error on an Amana refrigerator?
Repair costs vary depending on which component has failed. A replacement thermistor sensor is typically the least expensive fix, with parts generally ranging from $15 to $50. If the wiring harness requires repair or replacement, costs can range from $30 to $100 for parts. An L.V. control board replacement is the most expensive scenario, with parts typically ranging from $80 to $250, plus any labor charges if a technician performs the repair.

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