ErrorCodeDoctor
LG Air Conditioner CH66 error code
The CH66 error appears on LG inverter air conditioners and indicates a problem with how the indoor and outdoor units are connected — either the communication wiring or the refrigerant piping. If the error appeared right after installation or relocation it is very likely a connection issue that the installation technician needs to fix. If it appeared during normal use it may be a temporary fault caused by an unstable power supply and a power cycle may clear it. A persistent CH66 after resetting always requires a professional inspection.
Common causes
- Communication wiring between indoor and outdoor units was not connected correctly during installation
- Refrigerant piping connection is loose or incorrectly fitted
- Unstable power supply causing a temporary communication fault
- Wiring between units was damaged during relocation
How to fix it
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1
If the error appeared right after installation or relocation contact the installation technician immediately
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2
Ask them to inspect the communication line and piping connections between the indoor and outdoor units
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3
If the error appeared during normal use unplug the power cord or turn off the circuit breaker and wait 5 minutes
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4
Restore power and check if the error has cleared
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5
If CH66 keeps returning after a power cycle the unit needs inspection by a service technician
Related LG Air Conditioner error codes
CH66 error — frequently asked questions
What does the CH66 error mean on a LG air conditioner?
A fault was detected in the communication line or piping connection between the indoor and outdoor units
What causes the CH66 error?
The CH66 error is usually caused by: Communication wiring between indoor and outdoor units was not connected correctly during installation; Refrigerant piping connection is loose or incorrectly fitted; Unstable power supply causing a temporary communication fault; Wiring between units was damaged during relocation.
Can I fix the CH66 error myself?
This is rated a hard fix — it often requires tools, parts, or experience, and may be safer left to a professional technician.
How much does it cost to fix the CH66 error?
Fixing the CH66 error on a LG air conditioner typically costs $0–$200, depending on parts and whether you do it yourself or hire a technician.
Is it safe to keep using my air conditioner with the CH66 error?
We'd recommend addressing the CH66 error before continuing to use the air conditioner, since hard-rated issues often involve a real fault rather than a minor glitch.