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Error code reference

LG Hvac Error Code 46

PCB sees ODU suction line thermistor as open or shorted.

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PCB sees ODU suction line thermistor as open or shorted.

First step from the service manual

Must be 2,800Ω at 38°C/100°F & 10,000Ω at 10°C/50°F. Ohm thermistor in water; with perfect thermistor & plug connection, change PCB.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
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What 46 means on a LG hvac

Error code 46 on an LG HVAC system indicates that the outdoor unit (ODU) PCB has detected an abnormal signal from the suction line thermistor. The suction line thermistor monitors refrigerant temperature at the low-pressure side of the refrigerant circuit as gas returns to the compressor. The PCB continuously reads resistance from this sensor, and when the value falls outside the expected range, it interprets the thermistor as either open-circuit (infinite or very high resistance) or shorted (near-zero resistance), triggering this fault code.

The thermistor is a negative temperature coefficient (NTC) sensor with specific calibrated resistance values: 10,000 ohms at 10 degrees Celsius (50 degrees Fahrenheit) and 2,800 ohms at 38 degrees Celsius (100 degrees Fahrenheit). Any reading that deviates significantly from this curve points to sensor failure, wiring damage, or connector issues. Diagnosing this code correctly requires removing the thermistor and testing it submerged in water at a known temperature to get an accurate ohm reading free of ambient air interference.

If the thermistor resistance tests within specification at the appropriate temperature and the wiring harness and connector show no signs of damage, corrosion, or poor contact, the PCB itself is likely misreading the signal and will need to be replaced. This is a logical process of elimination: confirm the sensor is good, confirm the wiring is intact, and if both check out, the fault lies in the control board.

Source: manufacturer service documentation.

Common causes of 46

  1. 01

    Failed suction line thermistor

    Part replacement

    The thermistor itself has drifted out of spec or failed entirely, producing resistance values outside the expected 2,800 ohm at 38C or 10,000 ohm at 10C range. Testing the sensor submerged in water at a known temperature and comparing the reading to these benchmarks will confirm failure.

  2. 02

    Damaged or corroded thermistor wiring harness

    Part replacement

    Wiring between the thermistor and the PCB can become brittle, cracked, or corroded due to outdoor exposure, causing an open or intermittent circuit. Visually inspect the full length of the harness and check for continuity.

  3. 03

    Loose or corroded connector at the PCB or sensor

    Wiring / connection

    A poor connection at either the thermistor plug or the PCB header can simulate an open or shorted thermistor signal. Remove and reseat the connector, and inspect the terminals for oxidation or bent pins.

  4. 04

    Failed outdoor unit PCB

    Part replacement

    If the thermistor tests correctly at the specified resistance values and all wiring and connectors are intact, the PCB is likely misinterpreting the sensor signal. Board replacement is the final step after eliminating all other causes.

See the test procedure for each cause

Frequently asked questions about 46

What does 46 mean on a LG hvac?
Error code 46 means the outdoor unit control board (PCB) has detected that the suction line thermistor is reading as open-circuit or shorted. The suction line thermistor monitors refrigerant temperature on the low-pressure side of the system as it returns to the compressor. The system uses this sensor reading for operational control, and an invalid signal causes the unit to fault out. The code points to a sensor, wiring, connector, or PCB issue on the outdoor unit.
Can I fix error code 46 on my LG HVAC myself?
A knowledgeable DIYer can inspect the wiring harness and reseat the connector at the thermistor and PCB, which costs nothing and occasionally resolves the fault. Testing the thermistor resistance requires a digital multimeter and knowledge of how to test the sensor submerged in water at a measured temperature, comparing results against 2,800 ohms at 38 degrees Celsius or 10,000 ohms at 10 degrees Celsius. Replacing the thermistor is a straightforward part swap. However, if the PCB needs replacement, most homeowners prefer to have a certified technician handle that step.
Is it safe to run my LG HVAC with error code 46 active?
The system will typically not operate normally while error code 46 is active, as the PCB cannot properly monitor suction line temperature. Attempting to force operation without a valid suction line temperature reading could allow the compressor to run under unmonitored refrigerant conditions. It is best to leave the unit off until the fault is diagnosed and resolved.
How much does it cost to repair error code 46 on an LG HVAC?
If only the suction line thermistor needs replacement, parts and labor typically fall in the range of $75 to $200 depending on the specific model and local labor rates. If the outdoor unit PCB is at fault, the repair cost increases significantly, often ranging from $300 to $700 or more depending on board pricing and labor. Getting a diagnostic visit from a certified technician first will clarify which component is responsible before committing to parts costs.
Will resetting my LG HVAC clear error code 46?
A power reset may temporarily clear the fault and allow the unit to restart, but if the thermistor, wiring, or PCB has an actual defect, the code will return quickly. Resetting without addressing the root cause does not fix the underlying problem and can delay proper diagnosis. The correct approach is to test the thermistor resistance, inspect the wiring, and address whichever component is outside of specification.

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