LG CH 66 error code

What it means

CH 66 is an inverter-model protection that LG says can detect communication trouble and piping-connection abnormalities between the indoor and outdoor units. It is especially important after new installation or relocation.

Urgency

Likely causes

1. Communication line connection issue between indoor and outdoor units
2. Piping connection issue between indoor and outdoor units
3. Miswiring or loose communication-line connection after installation
4. Temporary fault from unstable power or other electrical factors

Homeowner fix

If CH 66 appeared right after installation or relocation, do not keep trying to run the system; call the installer. During normal use, power cycle once at the breaker if you can do that safely.

When to call a pro

Call a licensed HVAC technician if CH 66 returns or appears after installation. Tell them LG identifies CH 66 as communication-line or piping-connection abnormality.

Repair vs replace

Installation and communication faults are usually repairable. Replacement is only worth comparing if diagnosis finds major board or sealed-system damage on older equipment.

• LG Mega R-32 9,000 BTU (115V)

  Mega R-32

• LG Mega R-32 9,000 BTU (230V)

  Mega R-32

• LG Mega R-32 12,000 BTU (115V)

  Mega R-32

• LG Mega R-32 12,000 BTU (230V)

  Mega R-32

For your technician

Technician note: verify communication-line terminations, miswiring, indoor/outdoor pairing, piping connections, and model-specific inverter diagnostics. Page context: LG maps this display to the Mega R-32 line; source: LG official support pages: [LG Air Conditioner] Guide to Error Codes; [LG Air Conditioner] How to Check Air Conditioner Error Codes; LG status-display help articles; LG Korea [LG Air Conditioner] Air conditioner error inquiry cross-check; display convention: match the letter C, letter H, and sixty six marker exactly before comparing neighboring codes.

Which systems show it

Mega R-32

Related troubleshooting

Use the symptom guide alongside the exact display code if the unit is flashing, cycling, or showing comfort symptoms.

Related codes

Source

Next step