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Error code reference

LG Hvac Error Code CA

PCB sees ODU discharge pipe thermistor as open or shorted.

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PCB sees ODU discharge pipe thermistor as open or shorted.

First step from the service manual

Ohm thermistor in water, measure water temperature; must be 244,000Ω at 20°C/68°F, 24,400Ω at 90°C/194°F. 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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  • Wiring diagram references and connector pinouts from the OEM service manual
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What CA means on a LG hvac

The CA error code on an LG HVAC system indicates that the outdoor unit's (ODU) discharge pipe thermistor has been detected as either open-circuit or short-circuit by the main PCB. The discharge pipe thermistor monitors refrigerant temperature at the compressor discharge line, which is a critical measurement point for protecting the compressor from overheating and ensuring the refrigeration cycle operates within safe parameters. When the PCB reads a resistance value outside the expected range for any valid temperature, it flags the CA fault and typically shuts down operation to prevent compressor damage.

The thermistor itself is a negative temperature coefficient (NTC) device with specific resistance targets: 244,000 ohms at 20 degrees Celsius (68 degrees Fahrenheit) and 24,400 ohms at 90 degrees Celsius (194 degrees Fahrenheit). A reading of near-zero resistance indicates a short circuit in the thermistor or wiring, while an infinite or very high resistance reading indicates an open circuit, such as a broken wire or a failed thermistor element. Both conditions prevent the PCB from calculating a valid temperature, triggering the CA code.

Diagnosis should begin with removing the thermistor and measuring its resistance while submerged in water at a known temperature, comparing the result to the specified values above. If the thermistor resistance matches the specification and the wiring harness connector shows no corrosion, pin damage, or intermittent contact, the fault likely lies with the PCB itself, which is misreading the valid signal. In that case, PCB replacement is the appropriate next step.

Source: manufacturer service documentation.

Common causes of CA

  1. 01

    Failed discharge pipe thermistor

    Part replacement

    The thermistor element itself has failed open or shorted internally. Confirm by measuring resistance in water at a known temperature: the reading should be 244,000 ohms at 20 degrees Celsius or 24,400 ohms at 90 degrees Celsius. Any significant deviation points to a defective thermistor.

  2. 02

    Damaged or broken wiring harness

    Part replacement

    Physical damage to the wiring between the thermistor and the PCB, such as chafing, rodent damage, or a broken conductor, can produce an open-circuit reading. Inspect the full wire run and connector for visible damage or broken pins.

  3. 03

    Corroded or loose connector

    Wiring / connection

    Corrosion at the thermistor connector plug or a poorly seated connector can create high resistance or intermittent contact that the PCB interprets as an open or short fault. Inspect the connector pins for green or white corrosion deposits and ensure the plug is fully seated.

  4. 04

    Faulty PCB

    Part replacement

    If the thermistor resistance measures correctly at the specified values and the wiring and connector are in good condition, the PCB's thermistor input circuit has likely failed. The board is misinterpreting a valid signal as an open or short condition, and replacement of the PCB is required.

See the test procedure for each cause

Frequently asked questions about CA

What does CA mean on a LG hvac?
The CA code means the outdoor unit's main control board is detecting the discharge pipe thermistor as either open-circuit or short-circuit. This thermistor monitors refrigerant temperature at the compressor discharge line. The system shuts down because it cannot safely operate without a valid temperature reading from this sensor. The fault points to either the thermistor itself, the wiring, or the PCB.
Can I fix a CA error on my LG HVAC myself?
A knowledgeable DIYer can inspect the wiring harness and connector for visible damage or corrosion, but accurate diagnosis requires an ohmmeter and the ability to test the thermistor in water at a known temperature to verify the 244,000 ohm at 20 degrees Celsius specification. Replacing the thermistor is a relatively straightforward repair, but accessing the outdoor unit's components and handling refrigerant-side parts may require a qualified technician depending on local regulations. PCB replacement, if needed, also requires correct identification of the board and safe handling of electronics.
Is it safe to run my LG HVAC with a CA error code active?
No, you should not attempt to bypass or ignore the CA error and run the system. The discharge pipe thermistor protects the compressor by monitoring high-temperature refrigerant leaving the compressor. Without a valid reading from this sensor, the system cannot prevent the compressor from overheating, which can cause severe compressor damage and potentially create a safety hazard. Keep the unit off until the fault is properly diagnosed and repaired.
How much does it cost to repair a CA error on an LG HVAC system?
Repair costs vary depending on the root cause. A replacement discharge pipe thermistor is typically an inexpensive part, and total repair costs including labor often range from around 100 to 250 dollars. If the PCB is the faulty component, parts alone can range from 150 to 500 dollars or more depending on the specific unit model, with additional labor costs on top. Getting a diagnostic visit from a certified technician first will clarify exactly which component needs replacement.
Will resetting my LG HVAC clear the CA error code?
A power reset may temporarily clear the CA code and allow the unit to attempt a restart, but if the thermistor, wiring, or PCB has a genuine fault, the code will return quickly once the system tries to read the sensor again. Resetting does not repair the underlying electrical or component failure. The fault must be diagnosed and the defective component replaced to permanently clear the CA code.

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