CH21
LG DC Peak (Overcurrent) Error in Outdoor Inverter Circuit

Outdoor unit or indoor display shows CH21 and the system will not run or stops quickly.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Shorted compressor windings, Shorted IPM (Intelligent Power Module) on outdoor PCB, Shorted outdoor fan motor, Wiring short between compressor/fan and PCB

How to Fix / Troubleshooting

Critical safety warning: CH21 involves high-voltage inverter electronics. Always shut off power at the disconnect and breaker. Do not touch capacitor terminals or power components without proper training and tools.

Basic checks a homeowner can do:

  • Power reset: Turn off power for 10 minutes, then restore. If CH21 returns immediately, leave the unit off.
  • Visual inspection: Remove the outdoor panel and look for burnt components, melted wires, or a burnt smell around the PCB and compressor terminals.
  • Check wiring: Ensure compressor and fan motor connectors are firmly seated and that no wires are shorted to the cabinet.

Advanced diagnostics (technician level): Measuring compressor winding resistance, insulation resistance to ground, and testing the IPM module require specialized meters and should be done by a licensed HVAC technician.

Recommended action: Due to the risk of electric shock and further damage, CH21 faults should be handled by a professional. Likely parts include the outdoor PCB (inverter module), compressor, or outdoor fan motor.

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Repair Difficulty

Professional Required 5/5

Required Part

Outdoor Inverter PCB (IPM Module)
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