- HVAC
- Air conditioner
CH05
LG CH05 on an air conditioner: indoor and outdoor communication error
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On LG inverter air conditioners, CH05 (E0 or CH53 on some models) means the indoor and outdoor units are not communicating properly. Unplug or switch off the breaker, wait 5 minutes and restore power; if it stays, request service.
Safety first
Stop and check this first
- LG warns not to disassemble the air conditioner or replace internal parts yourself: it may cause fire, electric shock, serious injury or death. Boards, wiring and refrigerant are service technician work.
Safe checks you can perform
- Five-minute reset
- Demonstration mode on store units
- Checking cable and boards
Leave these tasks to a qualified professional
- Do not attempt this professional task: Check the wiring before replacing boards
- Do not attempt this professional task: Operating test
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Check the wiring before replacing boards
What they doThe technician checks the connecting cable and its terminals before proposing a board.
They must show youphotos of the terminals and the check result.
In writingwhat was corrected or which board was replaced and why.
Operating test
What they doAfter the repair the technician runs the unit and checks that CH05 does not return.
They must show youthe unit cooling or heating with no code.
In writingdate and result.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Five-minute reset
- Who:
- you.
- How:
- unplug the unit or switch off its breaker, wait 5 minutes and restore power, as LG instructs.
- Result that matters:
- whether CH05 reappears when it starts again.
- If it does not return:
- it was a one-off fault; note the date.
- If it returns:
- LG says to have a technician check it; stop resetting.
- Evidence to keep:
- a photo of the display with CH05 and a note of each occurrence.
Evidence: LG Air Conditioner - Guide to Error Codes · LG Air-Conditioner Error Codes: Checking code CH05
Demonstration mode on store units
- Who:
- you, if the unit is on display.
- How:
- LG says to use Demonstration Mode when the product is shown in a store without the outdoor unit running.
- Result that matters:
- whether the unit runs without its outdoor unit connected.
- If it is a display unit:
- enable Demonstration Mode and the code does not apply.
- If it is a real installation:
- continue with the technical check.
- Evidence to keep:
- nothing special; just the context of use.
Evidence: LG Air-Conditioner Error Codes: Checking code CH05
Checking cable and boards
- Who:
- an air conditioning technician.
- How:
- with power isolated, checks the cable between units and its terminals, then board communication.
- Result that matters:
- whether wires are loose or crossed or a board does not transmit.
- If a wiring fault is found:
- it is corrected and confirmed as the cause.
- If wiring is sound:
- it points to one of the boards.
- Evidence to keep:
- a job sheet with photos of the terminals and what was measured.
Requires isolating power and opening terminals on both units: technician only.
Evidence: LG Air-Conditioner Error Codes: Checking code CH05
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- LG
- Product type
- Air conditioner
Known code variants
- CH 05
- CH5
- CH53
- E0
- LG CH05
What it means
LG describes CH05 as the function that detects abnormal communication between the indoor and outdoor units of an inverter air conditioner. Its error code guide groups CH05, E0 and CH53 as the same type of error. LG only asks the owner for a power reset and, if the code stays, a technical check. The code does not say whether the cable between units, the indoor board or the outdoor board is at fault: the technician checks that by measuring.
Warnings and stop conditions
- Highsource verified
LG warns not to disassemble the air conditioner or replace internal parts yourself: it may cause fire, electric shock, serious injury or death. Boards, wiring and refrigerant are service technician work.
Evidence: LG Air-Conditioner Error Codes: Checking code CH05 · How to Troubleshoot Error Codes CH01, CH02, CH06 on Your LG Air Conditioner
Symptoms and causes
Probable causes · in order
- One-off communication dropPossible
A momentary interruption that clears after cutting power for 5 minutes; it shows because the code does not return after the reset.
Evidence: LG Air Conditioner - Guide to Error Codes · LG Air-Conditioner Error Codes: Checking code CH05
- Cable or connection between unitsPossible
If the code returns after the reset, communication is still failing; the technician checks the connecting cable and its terminals first.
Evidence: LG Air Conditioner - Guide to Error Codes · LG Air-Conditioner Error Codes: Checking code CH05
- Indoor or outdoor boardPossible
With correct wiring, the fault moves to the boards that send and receive the signal; only a technician's measurement separates them.
Evidence: LG Air Conditioner - Guide to Error Codes · LG Air-Conditioner Error Codes: Checking code CH05
Virtual technician
Does CH05 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
LG Air Conditioner - Guide to Error Codes
LG Electronics · 2026 · official_doc
- 2
LG Air-Conditioner Error Codes: Checking code CH05
LG Electronics · 2025 · official_doc
Was this entry useful?