LG mini split error code CH21
Inverter DC peak (IPM over-current). Also shown as CH 21, CH21.
- TypeProtection
- SystemCompressor / inverter
- Can I fix it?Technician job
What CH21 means on a LG
The inverter power module saw a current spike over its limit and shut down.
On this platform, CH21 is a protection: the system stopped or throttled itself to prevent damage; many clear on their own once conditions return to normal.
Common causes
- A blocked outdoor coil or failed fan.
- A shorted or failing compressor winding.
- A failed IPM.
- Loose compressor terminals.
How to fix it yourself
Do the reset and the visual checks, but the underlying repair needs a technician with a meter and the service manual.
- Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
- Look at the outdoor unit: clear leaves, cottonwood fluff, snow or ice from the coil and make sure the fan can spin freely and nothing is stacked against the cabinet.
- With power off, check the compressor terminals for loose or scorched connectors.
- Do not keep resetting.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
Technician diagnosis of the module and compressor.
Which LG units show CH21
This page applies to LG Art Cool, Standard, Mega and Multi F units. LG's own documentation lists CH21 as "Inverter DC peak (IPM over-current)", the same definition used across the LG it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where LG shows this code
The indoor display shows CH followed by a number (CH05, CH38). Units without a display blink the indicator lamps in a pattern; the outdoor board LEDs blink the same number. If someone tells you 'CH 5', that is CH05. CH01 to CH12 are indoor-unit faults, CH21 to CH29 are inverter and compressor faults, CH32 to CH38 are refrigerant-side protections, CH40 to CH48 are outdoor sensors, and CH51 to CH73 are outdoor-unit system faults.
Other LG codes
Same part of the system as CH21:
Questions people ask
Can I reset a LG CH21 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If CH21 comes back, the fault is real and needs the checks above.
Is it safe to keep running a LG showing CH21?
Not repeatedly. A protection code means the unit stopped itself to prevent damage, and resetting it over and over can turn a cheap repair into a compressor failure. Reset once, check the basics, and stop if it returns.
What will a technician check for CH21?
Technician diagnosis of the module and compressor. Ask for the measurements, not just a parts quote.
Sources
- LG residential split service manuals (error code tables)
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.