LG Air Conditioner CH 05 Error
What it means
CH05 (also shown as CH 05 or C5) is the most common LG air conditioner code. Per LG, it means a communication error between the indoor and outdoor units — the two units have stopped exchanging data. It's often a tripped breaker or a wiring/connection issue between the units.
Common causes of the CH 05 error
- Tripped breaker or interrupted power to the outdoor unit
- Loose, damaged, or miswired communication cable between indoor and outdoor units
- Power surge or brownout that desynchronized the two units
- Faulty indoor or outdoor PCB (control board) — less common
- Corroded or wet terminal block connections at the outdoor unit
How to fix the LG Air Conditioner CH 05 error
- 1Check the outdoor unit breakerLook at your electrical panel and see if the breaker feeding the outdoor unit has tripped. If so, that's likely the cause of the lost communication.
- 2Power-cycle both units together (LG's official step)Turn off the breakers for BOTH the indoor and outdoor units, wait 5 minutes, then turn them back on at the same time. This is the reset LG recommends for CH05.
- 3Visually inspect the connection wiringWith power off, check that the cable between the indoor and outdoor units is intact and not pinched, chewed, or corroded. Do not open terminal covers if you're not comfortable — leave that to a technician.
- 4Retry and observeRestart the unit and watch whether CH05 returns immediately or after running for a while; note this for the servicer.
🧰 When to call a professional
LG states that if CH05 persists after a power cycle, service is required. A licensed HVAC technician should check the communication wiring, terminal blocks, and control boards. Any work inside the electrical terminals or sealed system must be done by a licensed professional.
LG CH 05 error — FAQ
What does CH05 mean on an LG air conditioner?
CH05 is a communication error between the indoor and outdoor units — they've stopped talking to each other, often after a power interruption or a wiring fault.
How do I clear the CH05 error on my LG AC?
Turn off the breakers for both the indoor and outdoor units, wait 5 minutes, then switch them back on together. If CH05 returns, LG says service is required.
Is CH05 serious?
It can be minor (a tripped breaker that just needs a reset) or more involved (damaged wiring or a failed control board). If a power cycle doesn't fix it, have a technician inspect it.
Sources
This guide is independently written and not affiliated with LG. Always unplug appliances before servicing and follow your model's manual. Error codes and steps can vary by model — when in doubt, consult a qualified technician.