LG F4 error code

What it means

LG groups F4 with low-refrigerant protection on some models and also notes that some models display F4 for the CH 90/CH 91 test-run protection group. In either case, the official guidance points to installer or technician inspection if it persists.

Urgency

Likely causes

1. Low refrigerant detected on models where F4 matches CH 38
2. Test-run protection on models where F4 matches CH 90 or CH 91
3. Piping connection needing inspection after installation or relocation
4. Temporary fault from unstable power or other electrical factors

Homeowner fix

If F4 appears after installation or relocation, contact the installer. During normal use, turn the system off and do not keep resetting it if F4 reappears after one safe power cycle.

When to call a pro

Call a licensed HVAC technician if F4 returns or comfort is poor. Tell them LG lists F4 with low-refrigerant protection on some models and with CH 90/CH 91 test-run protection on others.

Repair vs replace

A setup or leak repair may be reasonable. If diagnosis leads to coil, line-set, compressor, or repeated refrigerant repairs on older equipment, compare the quote with replacement.

• 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: identify the model-specific F4 path first, then inspect refrigerant charge, piping connections, test-run status, and any leak indicators. 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 F and four 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