LG Air Conditioner CH05 Error Code: Meaning and How to Fix It
CH05 is a communication error: the indoor and outdoor units of your LG split air conditioner have stopped talking to each other properly for several minutes. It usually points to a wiring issue, a power problem at the outdoor unit, or a faulty control board.
A split AC works as a pair — the indoor unit and outdoor unit constantly exchange signals over a communication wire alongside the power cables. When those signals are lost or garbled for around three minutes, the system protects itself, stops, and shows CH05. Unlike filter or drain codes, CH05 often needs a technician, but you can safely rule out the simple causes first.
Common causes
- A tripped breaker or no power reaching the outdoor unit
- Loose, damaged or incorrectly wired communication cable between the units
- Electrical interference or a voltage problem
- A faulty indoor or outdoor PCB (control board)
- Damage to outdoor wiring from weather or rodents
How to fix it, step by step
- Check the breakers. Confirm both the indoor and outdoor unit breakers in your electrical panel are on. Outdoor units often have their own isolator switch near the unit — make sure it is on too.
- Do a full power reset. Turn the AC off at the breaker for at least 5 minutes, then restore power and restart. A confused control board sometimes recovers with a clean restart.
- Inspect visible outdoor wiring. With power off, look at the cable run to the outdoor unit for obvious damage, loose conduit or signs of pests. Do not open the unit's electrical cover yourself.
- Note when it happens. If CH05 appears only at certain times — storms, peak heat — tell the technician. Intermittent CH05 often means a marginal connection that expands and breaks contact with heat.
- Call an AC technician. Persistent CH05 after a reset and breaker check means the communication wiring or a PCB needs professional testing with a meter.
Do not keep resetting a CH05 unit day after day. Repeatedly running a system with a failing board or chafed wire can damage the compressor — the most expensive part of the whole AC.
Frequently asked questions
Is CH05 dangerous?
The AC shuts itself down safely, so it is not an emergency — but switch it off at the breaker if you see wiring damage or smell burning.
Can a power cut cause CH05?
Yes. Surges and brief outages can scramble communication between the units. A 5-minute breaker reset often clears it in that case.
How much does a CH05 repair cost?
A loose connection is a basic callout fee. A replacement PCB costs more, and the outdoor board is usually the pricier of the two.