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Error code reference

LG Refrigerator Error Code aS

Ambient (room temperature) sensor failure

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Ambient (room temperature) sensor failure - displayed when the room temperature sensor has a short or open circuit.

First step from the service manual

Check room temperature sensor resistance at POINT F voltage; 0V indicates short, 5V indicates open.

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

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What aS means on a LG refrigerator

The aS error code on an LG refrigerator indicates a failure in the ambient (room temperature) sensor circuit. This sensor monitors the temperature of the surrounding environment, and the refrigerator's control board uses that data to adjust compressor and fan operation accordingly. When the control board detects either a short circuit or an open circuit in this sensor's wiring loop, it triggers the aS code and displays it on the panel to alert the user and technician.

Diagnosing this fault begins at POINT F in the sensor circuit, where voltage is measured to determine the nature of the failure. A reading of 0V at POINT F indicates a short circuit condition, meaning the sensor or its wiring has collapsed the circuit to ground. A reading of 5V at POINT F indicates an open circuit, meaning the circuit path is broken entirely, which could result from a failed sensor element, a disconnected harness plug, or a wire that has broken internally. Each condition points toward a different root cause and repair path.

The ambient sensor itself is a thermistor, a resistive component whose resistance changes predictably with temperature. When the thermistor fails internally, it either loses all resistance (short) or infinite resistance (open), both of which produce out-of-range readings the control board cannot interpret. Wiring harness damage, corrosion at the connector pins, or a faulty control board can also produce the same fault signal, so each element of the circuit should be evaluated before replacing components.

Source: manufacturer service documentation.

Common causes of aS

  1. 01

    Failed ambient temperature thermistor

    Part replacement

    The thermistor itself has failed internally, producing either zero resistance (short) or infinite resistance (open). This is the most frequent cause and is confirmed by measuring sensor resistance and comparing it to expected values for the current room temperature.

  2. 02

    Open or broken wiring in the sensor harness

    Part replacement

    A wire in the harness connecting the ambient sensor to the control board may have broken internally or at a connector pin, causing the 5V open-circuit reading at POINT F. Visually inspecting the harness and testing continuity along each wire will reveal a break.

  3. 03

    Short circuit in the sensor wiring

    Part replacement

    Damaged wire insulation can cause two conductors to contact each other or contact ground, producing the 0V short-circuit reading at POINT F. Look for pinched, chafed, or heat-damaged sections of the harness routing.

  4. 04

    Corroded or disconnected connector

    Wiring / connection

    Corrosion or moisture at the sensor harness plug can increase resistance to the point of mimicking an open circuit, or can cause intermittent contact. Inspect the connector pins for discoloration, oxidation, or physical separation from the housing.

  5. 05

    Faulty main control board

    Part replacement

    If the sensor and all wiring test correctly, the control board's sensor input circuit may have failed, causing it to misread a valid signal as a short or open. This is the least likely cause and should only be considered after all other components are ruled out.

See the test procedure for each cause

Frequently asked questions about aS

What does aS mean on a LG refrigerator?
The aS code on an LG refrigerator indicates a failure in the ambient room temperature sensor circuit. The control board has detected either a short circuit (0V at POINT F) or an open circuit (5V at POINT F) in the sensor loop. This sensor helps the refrigerator adjust its operation based on the surrounding environment, so this fault can affect overall cooling performance if left unresolved.
Can I fix the aS error code myself?
A knowledgeable DIYer can start by checking the sensor's harness connector for loose pins, corrosion, or obvious wire damage, which sometimes resolves the issue without parts. If the connector looks intact, testing the thermistor's resistance with a multimeter and comparing it to expected values for room temperature can confirm whether the sensor itself has failed. Replacing the ambient sensor is a relatively straightforward repair, but if the wiring or control board is involved, professional diagnosis is recommended.
Is the aS error code dangerous? Can I still use my refrigerator?
The aS code is not a safety hazard in the traditional sense, and the refrigerator may continue to cool to some degree. However, without accurate ambient temperature data, the control board cannot optimize compressor and fan cycling correctly, which can reduce efficiency and potentially affect food preservation over time. It is best to address the fault promptly rather than relying on the appliance while the sensor circuit is compromised.
Will resetting my LG refrigerator clear the aS error code?
A power reset may temporarily clear the aS code from the display, but the code will return if the underlying sensor circuit fault is still present. Because the control board continuously monitors the sensor, any persistent short or open condition will trigger the code again within a short time after restart. A reset is useful for confirming whether the fault is intermittent, but it does not substitute for proper diagnosis and repair.
How much does it cost to repair the aS error on an LG refrigerator?
Repair costs depend on which component has failed. A replacement ambient temperature thermistor sensor typically costs between $15 and $50 for the part alone. If professional labor is included, or if the wiring harness or control board requires replacement, total repair costs can range from $100 to $350 or more depending on your location and the specific parts needed.

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