Inverter Compressor Phase Overcurrent
What it means
This code appears on LG inverter split air conditioners and on LG ducted and cassette units that use CH codes. It means the current in one of the three compressor phases went above its limit while running, so the outdoor inverter board stopped the compressor. Unlike CH21, which catches an instant spike, CH29 watches for excess current during operation, usually caused by mechanical or heat load on the compressor. The same code can mean something else on other brands.
Models covered: LG inverter split air conditioners (e.g. Dual Inverter) and LG ducted/cassette units that use CH codes; the code shows as CH plus a number on the display or as LED blinks.
Symptoms4
- The unit runs for a while, then CH29 shows and the compressor stops.
- Stops happen more in the hottest hours than at night.
- The compressor is louder than usual or the outdoor unit vibrates noticeably.
- Cooling is weak before the code appears.
Possible causes5
- High condensing pressure from a dirty condenser, a weak outdoor fan or poor ventilation around the outdoor unit.
- Refrigerant overcharge, or air and moisture in the system.
- Partly blocked electronic expansion valve or strainer increasing compressor load.
- Internal mechanical wear in the compressor or weak winding insulation.
- Loose compressor wiring or a faulty IPM on the outdoor PCB.
How to diagnose5
- Switch off the breaker for several minutes; make sure the outdoor unit is clean and its fan turns.
- A technician measures system pressures and pipe temperatures and compares them with LG specification.
- Measure compressor current while running against specification, and inspect compressor wires and terminals.
- Measure compressor winding resistance and insulation.
- Check the electronic expansion valve and the IPM per the service manual.
How to fix6
- Wash the condenser, improve ventilation around the outdoor unit and fix a weak outdoor fan.
- Correct the refrigerant charge by evacuating and weighing in, removing air and moisture (licensed technician).
- Replace a blocked electronic expansion valve or strainer.
- Repair compressor wiring or replace the outdoor PCB based on the tests.
- Replace the inverter compressor if internal damage is confirmed.
- Run the unit in hot conditions and monitor current, pressures and the code.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 150–5,000 (≈ USD 40–1,330)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
The low end is an outdoor unit wash or charge correction, the middle is an outdoor PCB or expansion valve, and the top is a new inverter compressor.
Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026
Frequently asked questions
What is the difference between CH21 and CH29?
CH21 catches a large instant current spike, often linked to the IPM. CH29 catches excess current while the compressor runs, usually from heat or pressure load on it.
Can too much refrigerant cause this code?
Yes. Overcharging raises pressure and compressor load, which raises current. Refrigerant should be charged by weight to the nameplate, not by guesswork.
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