ErrorCodeDoctor
LG Air Conditioner CH90 error code
The CH90 and CH91 errors appear on LG air conditioners and are most commonly triggered during the test run phase after a new installation or relocation. They act as a protective measure to prevent the unit from running when something is not set up correctly. On some models this code may appear as F4. If the error appeared during normal use rather than after installation it may have been caused by a temporary power issue and a reset will often clear it. A persistent error after resetting requires a technician.
Common causes
- Piping connections between indoor and outdoor units are incorrect or incomplete after installation
- Unit was relocated and piping was not reconnected correctly
- Unstable power supply triggering a false error during operation
- Fault detected in the refrigerant circuit during the test run
How to fix it
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1
If the error appeared after installation or relocation contact the installation technician immediately
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2
Ask them to check all piping connections between the indoor and outdoor units
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3
Their contact details are usually on a business card left during installation or on a sticker on the unit
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4
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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5
Restore power and check if the error has cleared
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6
If CH90, CH91, or F4 keeps returning after a power cycle contact a technician for inspection
Related LG Air Conditioner error codes
CH90 error — frequently asked questions
What does the CH90 error mean on a LG air conditioner?
A fault was detected during the test run phase to protect the unit from damage
What causes the CH90 error?
The CH90 error is usually caused by: Piping connections between indoor and outdoor units are incorrect or incomplete after installation; Unit was relocated and piping was not reconnected correctly; Unstable power supply triggering a false error during operation; Fault detected in the refrigerant circuit during the test run.
Can I fix the CH90 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 CH90 error?
Fixing the CH90 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 CH90 error?
We'd recommend addressing the CH90 error before continuing to use the air conditioner, since hard-rated issues often involve a real fault rather than a minor glitch.