LG CH05 Error Code: Indoor to outdoor communication failure
Updated October 2026 · Sourced from LG documentation
The indoor unit is not communicating with the outdoor unit. LG notes the error may be a temporary one caused by unstable electricity supply or other electrical factors. If it appears right after installation, LG says the installer should check that the communication cables are wired properly.
Is it safe to keep running? Check the steps below first. If the same symptom persists after a power reset, have it checked by a service technician.
CH05 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| CH05 Also: 5 On North American units, shown as blinking indicator LEDs (indoor unit, LED1 5 blinks); on other markets shown as the number 5 | Indoor to outdoor communication failure | LG single-split and multi-split air conditioners (North America LED blink code chart) |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Turn the power off or trip the breaker, and reset it about 5 minutes later.
- If it appeared right after installation, ask the installer to check the communication cable wiring.
🛑 Stop and call a licensed pro if
- If the same symptom persists after a power reset, have it checked by a service technician.
- Any code pointing to refrigerant, the compressor, high pressure or the outdoor unit board. Refrigerant work legally needs a certified technician.
- Burning smell, sparks, or a breaker that trips again after a reset.
- Water leaking from the indoor unit that does not stop after the drain is clear.
Safe first steps for any LG code
- Write down the exact code and how it shows (remote display or number of lamp blinks). Similar codes mean different things on different series.
- Turn the system off at the remote, switch off the breaker or disconnect for the unit, wait a few minutes, then turn it back on.
- Clean or replace the indoor unit air filters, and make sure nothing blocks the indoor or outdoor unit.
- Check that the condensate drain line is not blocked or kinked where you can see it.
- Replace the remote controller batteries if the display is dim or the unit does not respond.
Source: LG Single / Multi-Split Air Conditioner Error Codes (LG Canada help library), Error Code Chart. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician