LG CH05 Error Code: Causes & How to Fix It (2026)
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LG CH05 — quick diagnosis
CH05 = your LG indoor and outdoor units can't communicate (often shown as 5 indicator flashes). Confirm against your model's manual.
| Likely cause | How to spot it | What to do |
|---|---|---|
Communication wiring fault | CH05 returns after a reset | Technician — inspect the connecting cable & harness |
Outdoor unit lost power | Tripped breaker / blown fuse / bad socket | Restore power; reset breaker; test the fuse |
Power-up timing | CH05 after an outage or install | Power-cycle BOTH units off 5 min, on together |
Loose / mismatched terminals | Intermittent CH05 | Technician — check & match the wiring harness |
Outdoor control board (PCB) fault | Wiring is good but CH05 stays | Technician — board diagnosis |
The LG CH05 error code means an indoor-outdoor communication error — the two halves of your LG mini split or air conditioner have stopped exchanging signals. On many LG indoor units it also shows as the indicator light flashing five times. The most common cause is the connecting (communication) wiring between the units being loose, damaged, or mismatched, but it also comes from a power-supply problem (a tripped breaker, blown fuse, or bad socket on the outdoor unit) or a failed outdoor control board. LG’s own first step is a synchronized power cycle — cut power to both units for 5 minutes, then turn them on together so they re-link. If CH05 returns, the wiring or a board needs a licensed technician. Here’s the full breakdown.
What the LG CH05 code means
LG systems run a constant data link between the indoor and outdoor control boards over the connecting cable. When that signal is lost or unreadable, the unit reports CH05 (“CH” = Check) and usually stops heating or cooling until the link is restored. Because the indoor unit often signals it as 5 flashes of the operation light, count the flashes if you don’t have a digital display — but confirm against your model’s LG manual.
Common causes
- Communication wiring fault — loose, damaged, or mismatched connecting wires (the most common cause, especially after an install or repair).
- Power-supply problem — a tripped breaker, blown fuse, or faulty socket leaving the outdoor unit without stable power.
- Power-up timing — the units energizing at different times after an outage.
- Outdoor control board (PCB) fault — a defective transmit/receive circuit.
How to fix an LG CH05
- Power-cycle BOTH units together — switch OFF the breakers for the indoor and outdoor units, wait 5 minutes, then switch them both ON at the same time so they boot and re-link together. (This is LG’s recommended first step.)
- Confirm outdoor power — breaker not tripped, fuse and socket good. A dead outdoor unit reads as a communication loss; see outdoor unit not running.
- If CH05 returns, stop resetting and have a technician inspect the connecting wiring/harness and test the outdoor board.
When to call a professional
Looking at a different LG code? Our full LG error-code guide covers the CH-code list.
Sources
- LG USA Support — “Troubleshooting a CH05 error code” (indoor-outdoor communication; synchronized breaker reset). Confirm the exact steps for your model number.
Trademark note: “LG” is a trademark of LG Electronics. This page is an independent homeowner resource and is not affiliated with, authorized by, or endorsed by LG. Brand and code references are used factually for identification and troubleshooting only.
Frequently asked questions
What does the LG CH05 error code mean?
CH05 is a communication error between the indoor and outdoor units of your LG system — they've stopped exchanging signals. On many LG indoor units it shows up as the indicator light flashing five times. The usual causes are a wiring fault on the connecting cable, a power-supply problem (tripped breaker, blown fuse, bad socket), or a failed outdoor control board.
How do I fix an LG CH05 error?
LG's recommended first step is a synchronized power cycle: turn the system off, switch OFF the breakers for both the indoor and outdoor units for 5 minutes, then turn them both back ON at the same time so the units boot and re-link together. Also confirm the outdoor unit actually has power. If CH05 returns, the communication wiring or control board needs a technician.
Why does my LG keep showing CH05?
A repeating CH05 means a real fault is still present — most often a loose, damaged, or mismatched connecting wire between the indoor and outdoor units, a failing thermal fuse or power connection, or a faulty outdoor PCB. Power-cycling clears it briefly, but it returns until the wiring or board is repaired.
What does it mean when my LG indoor unit flashes 5 times?
Five flashes of the indoor unit's indicator light corresponds to the CH05 communication error on many LG models — the indoor and outdoor units can't talk to each other. Confirm the exact meaning against your model's manual, then start with the synchronized power cycle.
Can I fix LG CH05 myself?
You can safely do the power cycle and check that the breaker, fuse, and power connection to the outdoor unit are good. Inspecting or repairing the communication wiring and the control board means working at line-voltage terminals — that's a job for a licensed technician, especially if CH05 keeps coming back.