Air-source heat pump outdoor unit beside a house in the snow
9 components covered

Field manual · Air Conditioner

LG single-zone wall-mount ductless (Standard, Mega, Art Cool: LSN/LSU/LAN...HSV5 families): quick sheet

Covers: LG residential single-zone inverter heat pump wall-mount systems sold in North America, mainly the R-410A generation sold through about early 2025. Indoor units seen as LSN090HSV5, LSN120HSV5, LSN181HSV5, LSN240HSV5 (Standard / Mega style) and LAN...HSV5 (Art Cool mirror). Outdoor units seen as LSU...HSV5; system kits as LS...HSV5 (for example LS120HSV5 = LSN120HSV5 indoor + LSU120HSV5 outdoor, per distributor listings). Older look-alikes include LS...HSV, LSN...HSV and LS...HXV. The 3-digit number is nominal capacity in hundreds of BTU/h (090 = 9,000, 120 = 12,000, 180 = 18,000, 240 = 24,000). A distributor listing says the HSV5 family was discontinued in 2025 and replaced by R-32 equipment that is not cross-compatible. LGRED low-ambient branding: LG's LGRED page lists only cassette, air handler and ducted single-zone models, so no wall-mount LGRED model numbers are covered here. Search terms: LSN120HSV5, LSU120HSV5, LS120HSV5, LAN120HSV5, LG Art Cool, LG mini split CH05, CH10, CH21, CH38, CH67.

Cross-checkedBrands: LG9 components

LG wall-mount single-zone systems pair one inverter heat pump outdoor unit with one wall cassette and talk over the indoor-outdoor interconnect cable. Faults are reported as CH plus a number: models with a digit display show it on the indoor unit, others blink two LEDs on the indoor unit that have to be counted. LG's own pages say many codes shown at the indoor head actually start in the outdoor unit, so a code is a pointer, not a part order. All refrigerant-side work stays with an EPA 608-certified technician.

Safety first

  • All refrigerant work (charging, recovery, leak repair, brazing, compressor replacement, reading pressures for charge) is blocked: refer to an EPA 608-certified technician.
  • The outdoor inverter board's DC bus can hold a lethal charge for several minutes after power-off; verify 0 V DC before touching it.
  • Record the code before turning power off; power-cycling clears it on many boards.
  • Do not mix R-410A and R-32 indoor and outdoor units.

How it works

Power usually feeds the outdoor unit from a 208-230 V disconnect, and the outdoor unit powers the indoor head through the interconnect cable, which also carries the communication signal. If the boards stop hearing each other the indoor head shows CH05 (indoor side reporting) or CH53 (outdoor side reporting).

The indoor board reads a room-air thermistor and pipe (coil) thermistors, drives a brushless DC fan motor and the louver motors, and sends the call to the outdoor board. The outdoor board runs an inverter that varies compressor speed, a brushless DC outdoor fan, an electronic expansion valve and a reversing valve for heat mode.

The outdoor inverter monitors DC link voltage, compressor current, heat-sink temperature and discharge temperature. If one of these goes out of range it stops the compressor and reports a code in the 20s (inverter/compressor protection), 30s (discharge temperature), 40s (outdoor sensor open/short) or 60s (outdoor coil, heat sink, outdoor fan).

In heat mode the unit runs defrost cycles: the indoor fan pauses and the outdoor unit may steam. This is normal and is not a fault code.

On units without a digit display, LG's chart reads the code from two indoor LEDs (heating LED and cooling LED) blinking in a repeating sequence. LG's own chart is inconsistent about which LED is the tens digit and gives two codes the same pattern, so use the model's literature or LG support to decode blinks; a digit display or the LG ThinQ app is more reliable when available.

Components & tests

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Air-source heat pump outdoor unit beside a house in the snow by PeterEastern, CC BY-SA 4.0

Diagnostic guides for this appliance

Guide · Air Conditioner

PTAC not cooling (fan runs, air not cold)

Most PTAC no-cool calls are airflow (filter, coils), a wrong control setting or a failed compressor start component. Rule those out before suspecting the sealed system.

6 steps ~60 minmoderate
Guide · Air Conditioner

PTAC not heating (electric heat or heat pump)

PTACs heat with electric strip heat, a heat pump, or both. Heat pump models switch to strip heat in cold weather. Check settings, then the heater element and its limits, then the reversing valve.

5 steps ~60 minmoderate
Guide · Air Conditioner

PTAC error codes: how to read and clear them

Most PTAC brands store fault codes that can be shown with a button combination on the control (for example GE Zoneline uses a MODE + another key sequence on some models). Read the active code, fix the cause, then clear it.

4 steps ~20 mineasy

Other air conditioners manuals

Manual · Air Conditioner

Goodman / Amana GSX air conditioner and GSZ heat pump outdoor units: quick sheet

Goodman GSX (cooling-only condensers) and GSZ (split heat pumps), single-stage, 13-16 SEER class, plus Amana/Daikin badged equivalents. Heat pumps use a time-temperature defrost control board with selectable intervals.

7 components5 common failuresGoodman, Amana, Daikin
Manual · Air Conditioner

Carrier / Bryant split AC and heat pump outdoor units (single-stage): quick sheet

Carrier, Bryant and Payne single-stage split air conditioners (24-series style) and heat pumps (25-series style) with conventional 24 V control. Communicating Infinity/Evolution and variable-speed inverter units use different boards and are not covered.

7 components5 common failuresCarrier, Bryant, Payne
Manual · Air Conditioner

Trane XR14 / XR16 and American Standard Silver 14 / 16 outdoor AC and heat pumps (4TTR4, 4TTR6, 4TWR4, 4TWR6): quick sheet

Trane XR-series split outdoor units on R-410A: XR14 air conditioner 4TTR4 and heat pump 4TWR4 (1.5-5 ton, single-stage); XR16 air conditioner 4TTR6 and heat pump 4TWR6. Generation matters for the XR16: older 4TTR6 units (suffixes such as B or J, rated about 16 SEER) are single-stage; the 2023+ N-suffix units (e.g. 4TTR6036N1000A, 4TWR6036N1000A, up to 16.2 SEER2) are two-stage and are the former XR17 platform renamed XR16. American Standard equivalents: Silver 14 AC 4A7A4 (e.g. 4A7A4024N1000A) and Silver 14 heat pump 4A6H4 (e.g. 4A6H4048N1000A), both single-stage; 4A6H6 heat pump (older H-suffix Silver 16, single-stage); 4A7A6 AC stage count not confirmed. Also related: XR13 (4TTR3 / 4TWR3) single-stage. R-454B successors use a 5 prefix (5TTR4, 5TWR4, 5TTR6, 5A6H4, A5A6H6) and are not covered here. Search terms: 4TTR4, 4TTR6, 4TWR4, 4TWR6, XR14, XR16, Silver 14, Silver 16, 4A7A4, 4A6H4, 4A6H6.

8 components6 common failuresTrane, American Standard
LG single-zone wall-mount ductless (Standard, Mega, Art Cool: LSN/LSU/LAN...HSV5 families): quick sheet · OnCall Tech