HVAC Error Code LC — What It Means and How to Fix It

What Does This Error Mean?

HVAC error code LC typically means there is a drain blockage, float switch trip, or refrigerant leak detected. On Daikin units, LC specifically indicates a refrigerant leak check failure. On other brands, LC may mean the condensate drain float switch has triggered due to a full or blocked drain pan.

Affected Models

Daikin split systems
Daikin cassette units
Ceiling-mounted AC units
Cassette-type mini-splits

Common Causes

The condensate drain is clogged, causing water to back up and trip the float switch
The drain pan is overflowing because the drain pump is not working
The refrigerant leak sensor detected a drop in refrigerant pressure
The drain float switch wiring is loose or the switch itself has failed
Algae or debris has built up and blocked the condensate drain line

How to Fix It

Check the drain pan under the indoor unit. If you see standing water, the drain is blocked. This is the most common cause of LC.

A small amount of condensation in the pan is normal. Standing water that is overflowing or nearly full confirms a drain blockage.
Locate the condensate drain line — usually a small PVC pipe running from the indoor unit to a drain or outside. Clear any visible blockage at the outlet end.

Algae is the most common blockage. Pouring a cup of diluted bleach (1 part bleach to 10 parts water) into the drain access port kills algae and clears minor blockages.
If you have a wet-dry shop vacuum, attach it to the drain outlet outside and run it for 1–2 minutes to suction out the blockage.

This is the most effective DIY drain clearing method. It pulls debris toward the outside rather than pushing it deeper into the system.
Turn the unit off at the circuit breaker for 10 minutes to reset the float switch. Once the drain is clear and the pan water drains out, restart the unit.

The float switch automatically resets once the water level drops. The LC error should clear after a reset with a dry drain pan.
If the drain is clear and the pan is dry but LC still shows, call an HVAC technician. They will check the float switch wiring and test for refrigerant leaks.

Persistent LC on a dry system usually means a refrigerant issue or a faulty sensor — both require professional diagnosis.

When to Call a Professional

If the drain is clear but LC keeps returning, an HVAC technician needs to check the refrigerant system and inspect the leak sensor. Refrigerant leaks require professional repair — refrigerant handling is regulated by law. A blocked drain that you cannot clear yourself also needs a technician's snake or wet-vacuum tools.

Frequently Asked Questions

How often should I clean my AC drain line?

Clean your AC condensate drain at least once a year — ideally at the start of cooling season. In humid climates where the AC runs constantly, clean it every 3–6 months. Pouring diluted bleach into the drain access port monthly is an easy preventive measure that prevents algae buildup.

Will water damage happen if I ignore the LC error?

Yes. A blocked drain causes water to overflow the drain pan. This can damage ceilings, walls, and flooring — especially with ceiling-mounted cassette units. The float switch is there to prevent exactly this kind of damage. Do not ignore LC or try to defeat the float switch.

What is a float switch?

A float switch is a small safety device in the drain pan of your indoor AC unit. It works like the float in a toilet tank. When water rises too high, the float rises with it and triggers a switch that shuts down the AC. This prevents water from overflowing onto your ceiling or floors.