LG Mini-Split Not Heating: Causes and Fixes (2026 Guide)

If your LG mini-split is not heating, the most common causes are a mode setting issue, a defrost cycle in progress, or a dirty filter. In cold climates, the system's minimum operating temperature may also be a factor. This guide covers every cause and explains what to check, in order, before calling a technician.

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Check These First

1. Confirm HEAT mode. Press the MODE button on the LG remote until the sun icon appears. In AUTO mode, the system decides whether to heat or cool — if the room temperature already meets the setpoint, heating will not engage.

2. Check the setpoint. In heating mode, the setpoint must be higher than the current room temperature. If the room is at 70°F and the setpoint is 68°F, the compressor will not run.

3. Is "dF" showing on the display? dF means defrost — a normal cycle that occurs during heating mode in cold weather. The outdoor fan stops and the indoor unit blows cool air for 3–10 minutes. This is not a fault. Wait and heating will resume automatically.

Common Causes and Fixes

Temperature Limits: Standard vs LGRED°

Standard LG mini-splits are rated to operate in heating mode down to approximately −4°F (−20°C) at reduced capacity. The LGRED° cold-climate series maintains heating operation down to −13°F (−25°C). At temperatures below these ratings, output drops significantly or the system may stop operating entirely — this is by design, not a malfunction. For regions with regular sub-zero temperatures, the LGRED° model is the appropriate choice.

Frequently Asked Questions

Why does my LG mini-split blow cold air in heat mode?

The three most likely causes are: an active defrost cycle (temporary — wait 10 minutes), a stuck reversing valve (requires technician), or outdoor temperatures below the unit's rated minimum operating range. Defrost resolves on its own. A stuck reversing valve causes the system to continue operating in cooling mode even when heat is selected — the symptom is consistent cold air in heat mode regardless of outdoor temperature.

My LG LGRED° is not heating at −15°F — is that normal?

The LGRED° is rated to −13°F (−25°C). At −15°F (−26°C), you are below the unit's rated minimum — reduced or lost heating output at that temperature is within design limits. For the coldest nights that fall below the LGRED° rating, supplemental backup heat is the standard solution.

Related reading:
→ Do Mini-Splits Work in Cold Weather?
→ Mini-Split Not Heating? 8 Common Causes and Fixes
→ Mini-Split Heat Pump: How It Works, Costs and Best Brands