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Error code reference

LG Hvac Error Code 10

LS902HPV/LS122HPV/LA09xHV/LA12xHV

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LS902HPV/LS122HPV/LA09xHV/LA12xHV: PCB sees ODU discharge pipe thermistor open/shorted. All other Inverters/PTAC: ODU fan motor not rotating or not proving rotation. 10/13 SEER: IDU fan failure.

First step from the service manual

Discharge thermistor: must be 244,000Ω at 20°C/68°F & 24,400Ω at 90°C/194°F. Fan motor: verify 310V DC on motor wires; 0V DC=failed PCB, 310V DC=likely failed motor. Unplug and spin: 0V DC=motor caused board failure, 14-30V DC=good motor.

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

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What 10 means on a LG hvac

Error code 10 on LG HVAC systems covers two distinct fault conditions depending on the model. On LS902HPV, LS122HPV, LA09xHV, and LA12xHV units, the outdoor unit PCB has detected that the discharge pipe thermistor is either open-circuit or short-circuit. On all other inverter models and PTAC units, error code 10 indicates that the outdoor unit fan motor is not rotating or is failing to prove rotation to the control board. On 10/13 SEER systems, this code points to an indoor unit fan failure instead.

For the discharge thermistor fault, the sensor monitors refrigerant temperature at the compressor discharge line and is critical for protecting the compressor from overheating. A properly functioning thermistor should read approximately 244,000 ohms at 20 degrees Celsius (68 degrees Fahrenheit) and drop to approximately 24,400 ohms at 90 degrees Celsius (194 degrees Fahrenheit). Readings outside these values confirm a failed or disconnected thermistor. Wiring harness damage, connector corrosion, or thermistor degradation are common causes.

For the fan motor fault, the diagnostic process centers on DC bus voltage at the motor leads. The outdoor fan motor should receive 310 volts DC when commanded to run. A reading of 0 volts DC points to a failed control PCB that is not supplying drive voltage. If 310 volts DC is present but the motor does not run, the motor itself is the likely failure. To protect the board during diagnosis, the motor should be unplugged and spun manually: 0 volts DC measured after unplugging suggests the motor was back-feeding and causing board damage, while a reading of 14 to 30 volts DC confirms the motor is electrically sound.

Source: manufacturer service documentation.

Common causes of 10

  1. 01

    Outdoor fan motor failure

    Part replacement

    The outdoor unit fan motor has seized or lost its windings and is not rotating despite receiving 310V DC drive voltage from the PCB. This is confirmed when voltage is present at motor leads but the motor does not spin.

  2. 02

    Discharge pipe thermistor open or shorted

    Part replacement

    On applicable inverter models, the thermistor has failed or its wiring has been damaged, causing a resistance reading outside the expected range of 244,000 ohms at 20°C or 24,400 ohms at 90°C. Inspect the sensor and connector for corrosion or physical damage.

  3. 03

    Failed outdoor unit control PCB

    Part replacement

    If 0V DC is measured at the fan motor leads when the motor should be running, the PCB is not supplying drive voltage and has likely failed. This must be ruled out before replacing the motor.

  4. 04

    Fan motor back-feeding and damaging the PCB

    Part replacement

    A failing fan motor can feed voltage back into the control board, causing board damage. If the motor reads 0V DC after being unplugged and manually spun, the motor is the root cause of board damage and both components may need replacement.

  5. 05

    Wiring harness or connector issue

    Wiring / connection

    Loose, corroded, or broken connections at the thermistor plug or fan motor connector can cause the PCB to register an open or missing signal. Inspect all connectors in the circuit before replacing components.

See the test procedure for each cause

Frequently asked questions about 10

What does 10 mean on a LG hvac?
Error code 10 on LG HVAC systems signals one of two faults depending on the model. On LS902HPV, LS122HPV, LA09xHV, and LA12xHV inverter units, the outdoor PCB has detected an open or shorted discharge pipe thermistor. On all other inverter and PTAC models, it means the outdoor fan motor is not rotating or not confirming rotation to the board. On 10/13 SEER units, it indicates an indoor fan failure.
Can I fix error code 10 on my LG HVAC myself?
Some basic checks, such as inspecting wiring connectors for corrosion or physical damage, can be done by a knowledgeable homeowner. However, diagnosing this fault properly requires measuring DC bus voltage (up to 310V DC) at motor leads and testing thermistor resistance with a multimeter, which involves live high-voltage circuits. These steps should be performed by a qualified HVAC technician.
Is it safe to keep running my LG unit when error code 10 is displayed?
No. Error code 10 indicates either a missing temperature sensor input or a fan motor that is not operating. Running the system without a functioning discharge thermistor removes compressor overheat protection, and operating without proper fan airflow can cause refrigerant pressures to reach unsafe levels. The unit should remain off until the fault is diagnosed and repaired.
How much does it cost to repair LG HVAC error code 10?
Repair costs vary depending on the failed component. A replacement discharge pipe thermistor typically costs in the range of $20 to $80 for the part, while an outdoor fan motor can range from $80 to $250 or more depending on the model. Control PCB replacement is generally the most expensive repair, often falling between $150 and $500 for parts alone. Labor costs will add to these figures.
Will resetting my LG HVAC clear error code 10?
A power reset may temporarily clear the error code, but it will return as soon as the system attempts to run and detects the same fault condition. If the thermistor is out of spec, the fan motor is not rotating, or the PCB is not supplying proper voltage, the underlying problem must be repaired for the code to stay clear. Repeated resets without repair can lead to additional component damage.

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