LG air conditioner CH05 code: indoor and outdoor units not communicating (mini-split)

On LG mini-splits, CH05 means the indoor unit and the outdoor unit have lost communication. LG says the most common cause is a tripped breaker for the outdoor unit, so the indoor unit has power but the outdoor unit does not.

Likely causes

Listed from most to least common.

1. Circuit breaker or disconnect for the outdoor unit tripped or switched off
2. Brief power cut or surge that left the two units out of step
3. Loose or damaged communication wiring between the indoor and outdoor units
4. Indoor or outdoor control board fault

How to fix the CH05 code

Unplug the air conditioner or switch it off at the breaker before removing any panel or filter.

1. 1

   Step 1: Check the outdoor unit's breaker

   Look at your electrical panel. Many mini-splits have a separate breaker for the outdoor unit. If it has tripped, the indoor unit can still light up while the outdoor unit sits dead.

2. 2

   Step 2: Turn both breakers off

   Switch off the breaker for the indoor unit and the outdoor unit. LG advises waiting at least 3 to 5 minutes.

3. 3

   Step 3: Turn both back on together

   Switch both breakers back on at the same time, then start the unit with the remote. Give it a few minutes to start cooling.

4. 4

   Step 4: Watch for repeat trips

   If the outdoor breaker trips again, leave it off. A breaker that keeps tripping points to an electrical fault.

You'll need: Flashlight.

When to call a technician

Call a licensed HVAC technician if there is no separate outdoor breaker, the breaker keeps tripping, or CH05 returns after a reset. The wiring and boards need testing with the power on, which is not a DIY job.

A typical repair for this code costs $150–$600 in the US, including parts and labor. Prices vary by area and model.

Models this applies to

• Ductless mini-splits (wall-mounted and Art Cool)
• Multi-zone mini-split systems
• Window air conditioners
• Portable air conditioners

Codes can differ slightly between models. Your owner's manual is the final word and is available from LG support.

Common questions