DC Link Low Voltage

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 DC link voltage inside the outdoor inverter board, which feeds the IPM and the compressor, has dropped below its limit. The unit stops the compressor for protection and tries again when the voltage recovers. The exact wording can vary between outdoor unit generations, and 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.

Related codes: CH22CH21CH05CH26

Symptoms3

• CH23 shows and the compressor stops suddenly.
• The code repeats when the supply is weak or other large appliances switch on.
• The unit may run normally once the supply is stable, then the fault returns.

Possible causes5

• Low supply voltage or frequent short power dips.
• Loose or burnt power terminals at the outdoor unit or the breaker.
• Undersized or very long supply cable that lets voltage sag under load.
• Fault in the rectifier, smoothing capacitors or reactor on the outdoor inverter PCB.
• Faulty voltage sensing circuit on the outdoor PCB.

How to diagnose5

1. Switch off the breaker for several minutes, restart, and note whether the code matches times of weak supply.
2. A technician measures the supply voltage at the outdoor unit terminals with the compressor running and compares it with the nameplate range.
3. Check terminal tightness, the breaker and the supply cable size.
4. After discharge, inspect the outdoor board for swollen capacitors or burn marks.
5. Measure the DC link voltage per the LG service procedure, with great care because it is a high, dangerous voltage.

How to fix5

1. Tighten or replace damaged terminals and the breaker.
2. Fit a voltage protector rated for the unit if the supply is weak.
3. Replace the supply cable with one sized for the distance and load.
4. Replace the outdoor PCB if the incoming voltage is good and the fault is in the rectifier or smoothing section.
5. Run the unit and confirm stable operation without the code at peak times.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

When the cause is weak supply or a loose terminal, a voltage protector or connection repair is cheap; the top of the range is a new outdoor inverter PCB.

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