LG Mini-Split: 5 Flashes
A LG mini-split LED pattern starting with 5 flashes matches 4 documented codes: CH05, CH51, CH53, CH54. Watch the full pattern (short vs. long flashes) to tell them apart — all 4 are explained below.
Code CH05: Communication error between the indoor unit and the outdoor unit
Communication error between the indoor unit and the outdoor unit. The indoor unit's control board is not receiving a signal from the outdoor unit. This is the single most common LG mini-split code and it usually means the outdoor unit has no power or the interconnecting wiring is wrong or loose.
Manual wording: “Indoor unit PCB is not receiving signal from outdoor unit.”
Documented for: All LG residential mini-splits, single-zone and multi-zone
Likely causes, most common first
- No power on the indoor unit
- Indoor/outdoor unit power connection error, or the communication line was never installed
- Improper connection at the terminal block for the communication wire
- Improper wiring of the communication L-N wire between indoor and outdoor units
- Communication error caused by external electrical noise
- Indoor/outdoor communication circuit parts burned, or no power due to a burned indoor or outdoor PCB
What you can safely check yourself
- Check the breakers for BOTH the indoor and outdoor unit are on and not tripped
- Check the outdoor disconnect switch next to the condenser is switched on
- Turn the system off at the breaker for one minute, then back on
When to call a technician
If power is confirmed on at both units and CH05 stays, the interconnecting communication wiring or one of the control boards is at fault. Terminal-block and low-voltage work is a technician job.
A LG mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Single Zone Four-Way Ceiling-Cassette Installation Manual (LG Electronics U.S.A., Inc., Single-zone four-way ceiling cassette indoor units with LUU090HV through LUU420HV outdoor units) · checked 2026-08-25
- MULTI F / MULTI F MAX Outdoor Unit Installation Manual (LG Electronics U.S.A., Inc., Multi F and Multi F MAX multi-zone heat pump outdoor units (LMU series) with standard wall-mount, Art Cool, cassette and ducted indoor units) · checked 2026-08-25
- Convertible Mid-Static Ducted LGRED Degree System Installation Manual (LG Electronics U.S.A., Inc., LGRED single-zone convertible mid-static ducted indoor units with LUU180HHV / LUU240HHV outdoor units) · checked 2026-08-25
- Defining Common Error Codes - Standard Wall-Mounted High-Efficiency Single Zone Systems (LG Electronics U.S.A. - Commercial Air Conditioning, LS091HSV and LS121HSV systems (LSN091HSV / LSN121HSV indoor units, LSU091HSV / LSU121HSV outdoor units)) · checked 2026-08-25
- Room Air Conditioner SVC Manual (General) - Trouble Shooting Guide with Error Code (LG Electronics, All LG single-zone room air conditioner / mini-split chassis (SW, SB, SC, S4, S5, SH, SA, SJ, SK)) · checked 2026-08-25
Code CH51: Over capacity / combination ratio out of range
Over capacity / combination ratio out of range. The total capacity of the connected indoor units is under 50% or over 130% of the outdoor unit's capacity. On multi-zone systems this is an installation or wiring mistake, not a component failure.
Manual wording: “Combination ratio (capacity) is out of range; Total nominal indoor unit capacity is <50% or >130% of the outdoor unit capacity”
Documented for: LG Multi F / Multi F MAX multi-zone systems, and single-zone systems with a mismatched indoor/outdoor pair
Likely causes, most common first
- Mis-wiring between indoor and outdoor units
- Wrong wiring or piping connection during installation of several similar models at the same site (zone A's pipe run connected to zone B's wiring)
- Indoor units connected that add up to too little or too much capacity for the outdoor unit
When to call a technician
CH51 means the system was put together in a combination LG does not allow, or the zone wiring and piping were crossed at install. The installer needs to come back and verify each indoor unit's wiring matches its piping.
A LG mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- MULTI F / MULTI F MAX Outdoor Unit Installation Manual (LG Electronics U.S.A., Inc., Multi F and Multi F MAX multi-zone heat pump outdoor units (LMU series) with standard wall-mount, Art Cool, cassette and ducted indoor units) · checked 2026-08-25
- Single Zone Four-Way Ceiling-Cassette Installation Manual (LG Electronics U.S.A., Inc., Single-zone four-way ceiling cassette indoor units with LUU090HV through LUU420HV outdoor units) · checked 2026-08-25
- Convertible Mid-Static Ducted LGRED Degree System Installation Manual (LG Electronics U.S.A., Inc., LGRED single-zone convertible mid-static ducted indoor units with LUU180HHV / LUU240HHV outdoor units) · checked 2026-08-25
- Room Air Conditioner SVC Manual (General) - Trouble Shooting Guide with Error Code (LG Electronics, All LG single-zone room air conditioner / mini-split chassis (SW, SB, SC, S4, S5, SH, SA, SJ, SK)) · checked 2026-08-25
Code CH53: Communication failure from the outdoor unit to the indoor unit
Communication failure from the outdoor unit to the indoor unit(s). Same fault family as CH05, but reported from the outdoor side - the outdoor board is not hearing the indoor unit.
Manual wording: “Communication failure between outdoor unit and indoor unit(s)”
Documented for: All LG residential mini-splits, single-zone and multi-zone
Likely causes, most common first
- No power on the indoor unit
- Indoor/outdoor unit power connection error, or the communication line not installed
- Improper connection at the terminal block for the communication wire
- Improper wiring of the communication L-N wire between indoor and outdoor units
- Communication error caused by external electrical noise
- Indoor/outdoor communication circuit parts burned, or no power due to a burned indoor or outdoor PCB
What you can safely check yourself
- Check the breakers for BOTH the indoor and outdoor unit are on and not tripped
- Check the outdoor disconnect switch next to the condenser is switched on
- Turn the system off at the breaker for three minutes, then back on
When to call a technician
If power is on at both units and CH53 stays, the interconnecting wiring or a control board is at fault. That is technician work.
A LG mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- MULTI F / MULTI F MAX Outdoor Unit Installation Manual (LG Electronics U.S.A., Inc., Multi F and Multi F MAX multi-zone heat pump outdoor units (LMU series) with standard wall-mount, Art Cool, cassette and ducted indoor units) · checked 2026-08-25
- Single Zone Four-Way Ceiling-Cassette Installation Manual (LG Electronics U.S.A., Inc., Single-zone four-way ceiling cassette indoor units with LUU090HV through LUU420HV outdoor units) · checked 2026-08-25
- Convertible Mid-Static Ducted LGRED Degree System Installation Manual (LG Electronics U.S.A., Inc., LGRED single-zone convertible mid-static ducted indoor units with LUU180HHV / LUU240HHV outdoor units) · checked 2026-08-25
- Defining Common Error Codes - Standard Wall-Mounted High-Efficiency Single Zone Systems (LG Electronics U.S.A. - Commercial Air Conditioning, LS091HSV and LS121HSV systems (LSN091HSV / LSN121HSV indoor units, LSU091HSV / LSU121HSV outdoor units)) · checked 2026-08-25
- Room Air Conditioner SVC Manual (General) - Trouble Shooting Guide with Error Code (LG Electronics, All LG single-zone room air conditioner / mini-split chassis (SW, SB, SC, S4, S5, SH, SA, SJ, SK)) · checked 2026-08-25
Code CH54: Open phase / reverse phase error - the outdoor unit's incoming power is missing a leg or wired in the wrong order
Open phase / reverse phase error - the outdoor unit's incoming power is missing a leg or wired in the wrong order. LG's consumer page notes this usually shows up after a power outage or electrical work.
Manual wording: “Outdoor unit is not wired properly (ex: reversed phase)”
Documented for: All LG residential mini-split outdoor units
Likely causes, most common first
- Outdoor unit is not wired properly (for example, reversed phase)
- A power leg lost or reconnected in the wrong order after an outage or electrical work
What you can safely check yourself
- Check the breaker feeding the outdoor unit is fully on and not partially tripped
- Check the outdoor disconnect switch is fully seated and on
When to call a technician
If this appeared after a power outage, a panel change, or any electrical work, an electrician or HVAC technician needs to confirm the incoming power was reconnected correctly. Do not open the outdoor unit's electrical box.
A LG mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- MULTI F / MULTI F MAX Outdoor Unit Installation Manual (LG Electronics U.S.A., Inc., Multi F and Multi F MAX multi-zone heat pump outdoor units (LMU series) with standard wall-mount, Art Cool, cassette and ducted indoor units) · checked 2026-08-25
- Single Zone Four-Way Ceiling-Cassette Installation Manual (LG Electronics U.S.A., Inc., Single-zone four-way ceiling cassette indoor units with LUU090HV through LUU420HV outdoor units) · checked 2026-08-25
- Convertible Mid-Static Ducted LGRED Degree System Installation Manual (LG Electronics U.S.A., Inc., LGRED single-zone convertible mid-static ducted indoor units with LUU180HHV / LUU240HHV outdoor units) · checked 2026-08-25
- LG Air Conditioner - Guide to Error Codes (LG USA Support help library) (LG Electronics U.S.A., Inc., LG residential single-split and multi-split air conditioners / heat pumps) · checked 2026-08-25