LG · Split air conditioners · LG wall-mounted Inverter air conditioners (RAC) – CH codes
CH66Communication line or piping connection issue between indoor and outdoor units
Name in the manufacturer's documentation (service manual): Communication line or piping connection issue between indoor and outdoor units
[1]
In plain words (editorial)
A problem with the communication line or the piping connection between the indoor and outdoor units.
When to call a service technician: If the error appeared right after installation, contact the installation technician.
✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.
For technicians
Possible causes (source text)
- An issue with the communication line or piping connection between the indoor and outdoor units[2]
Steps given by the manufacturer (source text)
- If the error appeared immediately after installation, please contact the installation technician[3]
⚠ Work on refrigerant circuits, mains electricity and PV DC wiring is for qualified technicians only.
The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →
Sources
Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.
- [1] LG USA Support – [LG Air Conditioner] Guide to Error Codes (help library, 2026-02-23) – text capture , p. 2 official manufacturer document quote verified
The CH66 error occurs when there is an issue with the communication line or piping connection between the indoor and outdoor units.
- [2] LG USA Support – [LG Air Conditioner] Guide to Error Codes (help library, 2026-02-23) – text capture , p. 2 official manufacturer document quote verified
the ch66 error occurs when there is an issue with the communication line or piping connection
- [3] LG USA Support – [LG Air Conditioner] Guide to Error Codes (help library, 2026-02-23) – text capture , p. 2 official manufacturer document quote verified
if the error appeared immediately after installation, please contact the installation technician.