What it means
LG Canada's chart says 'DC peak error / IPM fault; compressor DC voltage was too high.' LG's US page groups CH21 with CH23, CH26 and CH29 as outdoor compressor or circuit board problems.
What to check, in order
- Reset the power
Unplug the unit or switch off its breaker, wait about 5 minutes, then switch it back on and see if the code clears.
- Stop using it if it returns
LG says that if the same code comes back, stop using the unit and request service to prevent further damage.
- Pass the code on
LG Canada suggests giving the code to your installer so they can diagnose it.
When to call an engineer
LG lists a temporary power issue, a faulty compressor, a compressor drive or protection circuit error, or a faulty electrical part in the outdoor unit as possible causes. This needs a technician.
A repair visit will usually check the compressor, its wiring and the inverter board that drives it.
- Note the model and serial number. They're on a label on the side of the indoor unit, and on the outdoor unit.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Quick answers
What does the LG CH21 error code mean?
The outdoor unit's compressor drive has detected a fault and shut the compressor down. It can be a one-off power problem or a fault in the compressor or its board. LG Canada's chart says 'DC peak error / IPM fault; compressor DC voltage was too high.' LG's US page groups CH21 with CH23, CH26 and CH29 as outdoor compressor or circuit board problems.
Can I fix LG CH21 myself?
Engineer only (engineer visit). Start with: reset the power; stop using it if it returns; pass the code on. LG lists a temporary power issue, a faulty compressor, a compressor drive or protection circuit error, or a faulty electrical part in the outdoor unit as possible causes. This needs a technician.
Is LG CH21 worth repairing?
Get a quote first. If a reset doesn't clear it, the inverter board or compressor may be at fault, which can be expensive. Get a quote first.
Checked against
- LG Canada: Single / Multi-Split Air Conditioner Error Codes
- LG USA: How to troubleshoot error codes CH01, CH02, CH06, CH12, CH41 to CH48, E1, E2, E3, E7, E8, F2, F3, CH21, CH23, CH26, CH29 and E9
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.