LG CH 21 error code

What it means

CH 21 means the outdoor inverter power module or compressor drive has reported a fault. LG's support table points to compressor or inverter PCB failure, so this is not a homeowner repair.

Urgency

Likely causes

1. Compressor failure
2. Inverter PCB failure
3. Temporary operation error

Homeowner fix

Turn the system off and power cycle once at the breaker if you can do that safely. If CH 21 returns, do not keep resetting and do not open the outdoor unit.

When to call a pro

Call a licensed HVAC technician if CH 21 returns. Tell them LG identifies CH 21 as outdoor inverter compressor IPM failure involving the compressor or inverter PCB.

Repair vs replace

Inverter-board or compressor-drive repairs can be expensive. On older out-of-warranty systems, compare a major outdoor-board or compressor 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: diagnose inverter PCB/IPM, compressor condition, drive output, and related outdoor power circuits. 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 twenty one 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