LG LS120HSV5 Ductless Mini Split Problems & Error Codes — Overview
The LG LS120HSV5 / LSN120HSV5 ductless mini split uses inverter-driven compressor technology to provide efficient heating and cooling. The most frequent repair issue on this model family is the CH21 error code, which LG defines as a DC peak / IPM fault / compressor overcurrent condition in the inverter system. This fault means the outdoor unit’s inverter PCB detected abnormal compressor drive current or triggered a protection event in the drive stage, not a simple filter or remote problem.
Other common issues include blinking lamp codes (CH 00 requiring inspection per LG support documentation), power supply and wiring faults that starve the inverter, and restricted outdoor airflow that can push the compressor into overload protection. Because this platform relies on precise inverter control and high insulation standards (above 10 MΩ phase-to-ground per LG service specs), electrical problems in the compressor windings or IPM module account for the majority of no-cool and protection-shutdown calls.
Most Common Problems on This Model
- CH21 error code and unit shuts down Inverter PCB IPM fault, compressor overcurrent, or DC peak protection triggered by a failing compressor winding, bad inverter PCB, or power supply problem.
- Unit won’t start or blinking lamp (CH 00) Power supply issue, loose wiring connector, tripped breaker, or inverter PCB requiring inspection per LG support documentation.
- Compressor hums but won’t run Compressor electrical defect with unequal phase-to-phase resistance at U/V/W terminals or low insulation resistance below 10 MΩ to ground.
- Inverter board shows burn marks or carbonization IPM module failure, loose screw joints, or carbonized connector causing high resistance and heat, requiring inverter PCB replacement.
- Unit runs then stops on protection Restricted outdoor coil airflow, blocked installation space, or dirty coil causing inverter overload and compressor overcurrent shutdown.
- No cooling and low DC link voltage at inverter Incoming power supply fault or bad rectifier stage on inverter PCB (expect roughly 310 V DC single-phase or 540 V DC three-phase at P–N terminals).
- EEV harness fault contributing to protection shutdown Loose or corroded EEV coil connector at outdoor main PCB disrupting refrigerant control and triggering inverter protection per LG isolation steps.
- Abnormal diode readings between P and U/V/W phases Failed IPM or inverter output stage requiring inverter PCB replacement after confirming diode behavior as part of LG troubleshooting.
Parts That Commonly Fail
| Part | Notes |
|---|---|
| Inverter PCB / IPM module | Amazon | Fails with carbonization, burn marks, or DC peak / IPM fault triggering CH21 code. |
| Compressor | Amazon | Defective when phase resistance is unequal or insulation resistance drops below 10 MΩ to ground. |
| EEV coil harness | Amazon | Connector corrosion or loose seating at outdoor main PCB disrupts refrigerant control. |
| Power supply wiring and connectors | Amazon | Loose or undersized wiring causes voltage drop and inverter protection shutdown. |
When to Call a Pro
Call a licensed HVAC technician for any CH21 or protection code, compressor electrical testing (phase resistance and insulation resistance), or inverter PCB diagnostics. Measuring DC link voltage at P–N terminals (310 V DC single-phase, 540 V DC three-phase per LG specs), checking diode behavior between phases, inspecting for carbonization on the IPM, and performing compressor insulation tests above 10 MΩ all require a meter and refrigeration knowledge. Compressor or inverter PCB replacement also means recovering refrigerant, brazing, evacuation, and recharge, which are EPA-certified tasks. If you see burn marks, smell electrical odor, or the unit trips your breaker repeatedly, shut off power at the disconnect and call a pro immediately.