Lg Mini Split F4 Error Code

Updated 2026-08-29 · review status: manual-verified Last verified: 2026-08-29

Quick answer

On LG units, F4 points to low refrigerant levels (grouped by LG with CH32/33/36/38 on some models) or, on others, the CH90/91 test-run protection group. Stop using the unit - refrigerant work is technician-only, so reset once and call if F4 returns.

Severity: high · DIY difficulty: beginner

Safety

Stop after one power-cycle and, if the code appeared after installation or relocation, contacting the installer. Do not connect gauges, add or recover refrigerant, or open refrigerant circuits - R-32 sealed-system work is EPA-certified technician-only.

What F4 means

F4 is listed by LG with low-refrigerant protection on models where it matches the CH32/33/36/38 group, and on other models it belongs to the CH90/91 test-run protection group (incorrect wiring, incomplete test run, or restricted refrigerant flow). Either way, persistent F4 means installer or technician inspection.

Code meaning varies by series

  • Models where F4 matches the CH38 group: Low refrigerant detected - possible leak or undercharge
  • Models where F4 matches CH90/CH91: Test-run protection - incorrect wiring, incomplete test run, or restricted refrigerant flow (typically right after installation or relocation)

Causes, ranked

  1. 1. Low refrigerant from a leak (flare, braze joint, or coil leak) occasional pro-only

    Check: Oil residue or frost at line-set joints is a visual clue only; confirmation needs gauges and leak detection.

    Fix: Technician: leak-test, repair, recover and recharge to nameplate.

  2. 2. Restricted refrigerant flow during test run (new install or relocation) occasional pro-only

    Check: Restricted flow shows up in pressures and temperatures, not visible outside.

    Fix: Installer/technician: complete or correct the test run, verify line-set work and valve positions.

  3. 3. Incorrect or incomplete installation wiring (test-run group models) occasional diy-ok

    Check: If F4 appeared right after installation, do not troubleshoot yourself - contact the installer; they must complete the test run.

    Fix: Installer: correct wiring and finish the commissioning test run.

  4. 4. Temporary fault from unstable power or electrical factors occasional diy-ok

    Check: Power-cycle: turn the system off, restore power once, and observe.

    Fix: If F4 clears and stays cleared, monitor. Any recurrence stops DIY steps.

  5. 5. System undercharged at factory/installation (slow leak signature) occasional pro-only

    Check: Requires gauge readings and history of declining performance.

    Fix: Technician: verify charge against nameplate, find and fix the leak before topping up.

Related codes

lg/h38 · lg/h32 · lg/h67 · lg/h90

Commonly searched as: "lg f4" · "lg error code f4" · "lg air conditioner f4"

Sources

  • LG F4 error code - SplitAtlas — verified 2026-08-29
  • How to troubleshoot CH05, 53, E0, CH32-38, F4, CH66, 90-93 - LG USA Support — verified 2026-08-29