Indoor display shows CH04 and the unit may not start or may shut down shortly after starting.

Safety: Turn off power at the breaker before opening the indoor unit. Water and electricity together are hazardous.

Steps to address CH04:

• Check for water overflow: Remove the front cover and inspect the drain pan. If it is full of water, do not run the unit until the cause is found.
• Clear the drain line: Locate the condensate drain hose. Use a wet/dry vacuum at the hose outlet or gently blow compressed air from the indoor side to clear clogs (algae, sludge, debris).
• Inspect the drain pump (if equipped): Some LG indoor units have an internal pump. Check for kinks in the pump discharge line and ensure the pump is not jammed with debris.
• Check float/level sensor: Locate the float switch or water level sensor in the drain pan. Make sure it moves freely and is not stuck in the "high" position. Clean any slime or buildup.
• Verify wiring: Confirm that the pump and sensor connectors are firmly seated on the indoor PCB and that no wires are cut or corroded.
• Test operation: With covers still off but all wiring reconnected, briefly restore power and run the unit while observing the pump. Ensure it activates and removes water, then turn power back off.
• Replace components if needed: If the pump does not run or the float sensor does not change state when moved, replace the faulty LG drain pump or float/level sensor assembly.
• Reassemble: After confirming proper drainage, reassemble the unit and test for normal operation without CH04.

Call a technician if: The pump and sensor are functional but CH04 persists, as the indoor PCB or firmware may be defective.