Indoor unit shows E9 and may stop; sometimes associated with defrost or sensor issues.

Safety first: Turn off power before accessing the indoor unit drain pan.

Drain-related models:

• Check for water: Remove the front cover and inspect the drain pan. If full of water, the drain is likely clogged.
• Clear drain line: Locate the condensate drain hose. Use a wet/dry vacuum at the outlet outside to pull out sludge and algae. Flush with a mild vinegar solution if accessible.
• Inspect float switch: If equipped, ensure the float switch moves freely and is not stuck in the up position.

EEPROM-related models: If no water issue is found, E9 may indicate an internal PCB memory fault. In that case, replacement of the indoor main control board is typically required by a technician.