How an LG freezer signals trouble
LG upright freezers share the refrigeration control family, so when the cabinet drifts warm or the defrost system fails the freezer shows a short “Er” alert — often with the “Er” prefix dropped — rather than thawing silently. Because a freezer’s whole job is to stay deeply cold, the alerts that matter most are the fan and defrost faults. Reading them is the start of any LG freezer repair.
The alerts you will see
FF points at the freezer fan, which moves cold air through the cabinet; if it stalls, the cabinet warms even while the compressor runs. CF is the condenser fan, dH flags a defrost cycle running over an hour, and dS is the defrost sensor — on a freezer, defrost faults are the ones to watch, because a defrost failure lets frost smother the evaporator until airflow chokes. FS is the freezer temperature sensor.
Indicators and demo mode
Sb is Sabbath mode and is not a fault. As with the refrigerators, a freezer that appears not to cool may be in OF F demo mode, where lights are on but cooling is off; holding the indicated pads clears it. A telltale sign of a real defrost fault is heavy ice only on the rear wall while the rest of the cabinet looks normal — the subject of its own guide.
What to check, and when to call
For a warm cabinet, confirm the door seals fully, the unit is not overloaded with warm food and it is not in demo mode, then give it time to recover. A persistent FF or CF fan code, a dH defrost fault or a freezer that will not hold temperature needs an experienced technician with genuine parts. See the guides on a freezer not freezing and frost build-up, browse the error codes library, then book freezer repair. Confirm your model on the manufacturer’s site at lg.com/us.