LG Mini Split F4 Error Code

Updated 2026-08-30 · review status: manual-verified · reviewed by MiniSplitDecoder Editorial Team Last verified: 2026-08-30

Check your model first

  • Models where F4 matches the CH38 group
  • Models where F4 matches CH90/CH91

Match the model on your equipment label to the linked manufacturer documentation. The same code can mean different things across model families.

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: easy

Safety

Stop at the breaker power-cycle and any plug-accessible checks (filters, remote settings, visible wiring). The outdoor unit's capacitor holds a lethal charge and the refrigerant circuit is both pressurized and (on R-32 units) flammable — opening panels or servicing the sealed system is licensed-technician work (EPA 608).

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)

First checks before service

This page currently documents the safe reset triage. If the code returns, use the linked source manual or a qualified technician for code-specific diagnosis.

  1. 1. One-time fault event (power disturbance or transient sensor reading) common DIY

    Check: Power-cycle at the breaker/disconnect (or unplug for CPAP), restore, and run the system while watching for the code.

    Fix: If the code does not return after a full run cycle, the fault was transient — monitor, no repair needed.

  2. 2. Fault persists after a clean reset occasional pro only

    Check: If the code returns immediately or every session, note the conditions (startup, heating, after rain).

    Fix: A persisting code points at the component the manual assigns to this code — that repair is technician territory.

Related codes

Cross-references for the same fault family, by brand:

LG H38 · LG H32 · LG H67 · LG H90

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

Sources

Related Mini Split guides

Mini-Split Communication Error: DIY Checks · Mini-Split Flashing Light Decoder: Blink Patterns · Mini-Split Maintenance Checklist: Seasonal DIY Tasks · Mini-Split Not Cooling: Ranked Causes and DIY Checks