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haier | air-conditioner – CT Sensor Fault
Error Codes (undefined): Troubleshooting, Fixes & Prevention Tips explained below.

What Does CH40 Mean?❓

CH40 means that your LG AC’s current sensing system has detected irregularities in the compressor’s electrical load. This could be due to a malfunctioning CT sensor or an actual issue with the compressor’s current draw. It is a safety feature that helps protect the system from electrical overload or damage.

air-conditioner - Causes of CH40 Error

  • Faulty or disconnected CT sensor
  • Damaged wiring between CT sensor and main PCB
  • Abnormal compressor current draw
  • Loose connections or oxidized terminals
  • Defective inverter PCB or control board

air-conditioner - How to Fix CH40 Error❓

  • Inspect CT Sensor

    1. Turn off the unit and check the CT sensor for visible damage.
    2. Ensure sensor is securely connected to the control board.

  • Check Wiring

    1. Inspect wiring for disconnections, corrosion, or burns.
    2. Reconnect or replace wires as needed.

  • Test Compressor Current

    1. Use a clamp meter to check if the compressor current is within the normal range.
    2. If abnormal, investigate compressor health.

  • Replace Faulty Parts

    1. If sensor or PCB is faulty, replace with compatible LG parts.

air-conditioner - Helpful Tips

  • Never ignore electrical-related AC errors.
  • Only a technician with electrical experience should handle CT sensor diagnostics.
  • Always turn off the power supply before inspecting electrical components.
  • Schedule periodic system diagnostics to catch early sensor faults.
  • Don’t continue running the AC with this error—it can damage the control board.

Frequently Asked Questions❓

Question: What does the CT sensor do in an LG AC?
Answer: It monitors the current draw of the compressor to prevent electrical overload.
Question: Can a faulty CT sensor stop my AC from working?
Answer: Yes, because it’s tied to the protection mechanism. If it fails or misreads current, it can shut down the unit.
Question: Is CH40 dangerous?
Answer: While not immediately dangerous, ignoring it can lead to electrical or compressor damage.

When to Contact a Technician

If you experience any of the following issues even after completing the recommended troubleshooting steps, please contact an authorized service technician or our support team for further assistance.

  • The same error appears repeatedly after restarting or resetting the unit.
  • Multiple error codes appear simultaneously.
  • The device makes unusual noises, vibrations, or emits a burning smell.
  • The product fails to start, operate, or complete its function despite troubleshooting.
  • There are signs of electrical issues, physical damage, or leakage.
  • An unknown or unlisted error code appears on the display.

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