Error Code C2 in Air Conditioners

The C2 error code in air conditioners is primarily associated with three issues:

1. Malfunction of the outdoor unit temperature sensor.
2. Malfunction of the evaporator tube temperature sensor or indoor unit sensor.
3. Communication failure between the master control and the inverter compressor controller.

Below is a detailed description of each issue and possible solutions:

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1. Malfunction of the Outdoor Unit Temperature Sensor

This issue is common in many LG models. Possible causes include:

• The thermistor (sensor) is shorted or open.
• The thermistor is not connected to the indoor PCB (Printed Circuit Board).
• The thermistor’s resistance is incorrect.
• Damage or defect in the detection circuit of the indoor PCB.

Steps to Resolve the Issue:

• Turn off the equipment: Disconnect the power for a few minutes and check if the error code disappears.
• Inspect the sensor and wiring: Check for visible damage to the sensor or its cables.
• Verify connection: Ensure the sensor is properly connected to the control board.
• Measure the thermistor resistance:
  1. Turn off the equipment and disconnect the sensor.
  2. Use the multimeter’s kilo-ohm scale to measure resistance. Compare the reading with the sensor’s resistance-temperature chart, if available.
  3. Rub the sensor with your hand; the measured resistance value should decrease.
  4. Resistance readings should never show zero or infinity.
• Check the sensor voltage:
  1. Turn on the equipment, reconnect the sensor, and measure the voltage using the multimeter’s DC voltage scale. Expect a reading near 2.5 volts.
• Inspect PCB resistance:
  1. With the control board powered off, inspect the resistance near the sensor connector.
  2. If the measured resistance is incorrect, replace the resistor on the board.
• Replace the outdoor PCB: If all else fails, replace the outdoor unit’s control board.

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2. Malfunction of the Evaporator Tube Temperature Sensor

This issue is common in Samsung models. To resolve the problem, follow the same steps as outlined for the outdoor temperature sensor. However, in this case, the control board that manages the temperature sensor is located in the indoor unit.

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3. Communication Failure Between the Master Control and the Inverter Compressor Controller

This issue is commonly found in Gree models.

Steps to Resolve the Issue:

• Turn off the equipment: Disconnect it from power for a few minutes.
• Reconnect the equipment: Check if the error persists.
• Verify the power supply: Measure the voltage from the external power grid, ensuring it is within a 10% error margin.
• Inspect signal cable connections: Ensure all signal cables are securely connected.
• Perform a visual inspection of the PCBs: Look for visible damage to electronic boards and replace faulty components as needed.
• Check optocouplers: Communication issues between units are often related to optocouplers near the signal cable connection.

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